Hazard Plain Automated baseline

Mercer County, IL

Risk-assessment baseline packet

County FIPS:
17131
Release:
2026-10
Data as of:
2026-09-30
Storm Events data through:
2026-06-30

Hazard Plain is an independent product built from public federal data. It is not a FEMA document and is not reviewed or endorsed by FEMA or any state agency.

Hazard Plain release 2026-10, as of 2026-09-30.

Summary

Plan status as of 2026-09-30: Approved, expires 2029-06-03. Plan: Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636), approved 2024-06-04.

Since the plan was approved on 2024-06-04: no new hazard declaration and 25 NOAA Storm Events records; details under "What changed since your last plan".

Highest expected annual loss (FEMA National Risk Index, modeled total; see B1-a): Inland Flooding ($1,950,486 a year), Strong Wind ($1,209,116) and Drought ($907,319).

The tables that follow are organized by the items of FEMA's Local Mitigation Plan Review Tool, Element B (B1-a to B2-c); each heading says which item its tables support.

Plan clock

Status:
Approved, expires 2029-06-03
Plan:
Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)
Approved:
2024-06-04
Days to expiry:
977

What changed since your last plan (approved 2024-06-04)

New federal declarations:
none
Storm Events records since approval:
25 records (data through 2026-06-30)
Repetitive loss now:
FMA RL 0, SRL 1 (44 CFR 77.2); any definition: 3
Repeat-flood change:
this release sets the baseline count.

Sources: 1, 2, 4, 6 (numbered list at the end)

Plan status for every jurisdiction listed in this county: 13 rows, in the section "Plan clock: Plan status for every jurisdiction listed in this county" on the following pages.

State plan status and tribal plans in this state: see the state page.

Plan clock

Plan status for every jurisdiction listed in this county

Source: 1

JurisdictionTypeStatusPlanApprovedExpiresDays to expirynegative = days since expiry
Mercer CountyCountyApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Aledo cityCityApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Joy villageVillageApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Keithsburg cityCityApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Matherville villageVillageApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Sherrard villageVillageApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Abington townshipTownshipApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Preemption townshipTownshipApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Sherrard Community Unit School District 200School/School DistrictApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Aledo Fire Protection DistrictFire/EMS DistrictApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Genesis Medical CenterHospital/Medical FacilityApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Greene Township Fire Protection DistrictFire/EMS DistrictApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977
Sherrard Community Fire Protection DistrictFire/EMS DistrictApproved, expires 2029-06-03Mercer County 2024 Hazard Mitigation Plan (FEMA plan 109636)2024-06-042029-06-03977

Plan 109636 covers 1 other participant: Bay Island Drainage & Levee District (Warren County).

Supports FEMA checklist item B1-a: hazard identification

Hazards NRI does not cover (local data needed)

  • dam failure (incl. upstream dams)
  • levee failure
  • flash flood as its own subtype
  • ice jams
  • debris flows
  • erosion (riverine and coastal)
  • land subsidence and sinkholes
  • expansive soils

The 18 National Risk Index hazards, ranked by expected annual loss (EAL)

Sources: 5, 6

Rank by EALHazardNRI risk ratingEAL ratingEAL buildingsmodeled dollars per yearEAL agriculturemodeled dollars per yearCost of expected deaths and injuriesFEMA's dollar value per year, not property damageEAL total (see note)modeled dollars per yearStorm Events records, 1996 to 2026-06-30countStorm Events coverage note
1Inland FloodingVery LowVery Low$1,728,957$211,651$9,879$1,950,48655
2Strong WindRelatively ModerateRelatively Moderate$428,009$376,079$405,028$1,209,116108Includes 7 High Wind and 1 Strong Wind records (NOAA non-thunderstorm wind types, outside NRI's Strong Wind definition).
3DroughtRelatively ModerateRelatively Moderaten/a$907,319n/a$907,31915
4Cold WaveRelatively LowRelatively Low$83$397,852$378,773$776,70817Includes 5 Frost/Freeze records (outside NRI's Cold Wave definition; counted in this table and in B1-d, not in the B1-e descriptor).
5Heat WaveRelatively LowRelatively Low$3$7$551,210$551,2205
6LightningRelatively ModerateRelatively Moderate$2,632n/a$489,286$491,9173
7TornadoVery LowRelatively Low$128,935$1,456$336,963$467,35335
8Ice StormRelatively ModerateRelatively Moderate$42,722n/a$242,493$285,2159
9HailVery LowRelatively Low$155,285$5,723$21,208$182,21672
10EarthquakeVery LowVery Low$35,756n/a$32,851$68,607Storm Events does not record earthquakes.
11Winter WeatherRelatively LowRelatively Low$507$1,306$38,494$40,307124
12LandslideRelatively LowVery Low$106n/a$7,619$7,7250No recorded events in Storm Events since 1996 (data through 2026-06-30).
13HurricaneVery LowVery Low$318$3,446under $1$3,7640No recorded events in Storm Events since 1996 (data through 2026-06-30).
14WildfireVery LowVery Low$356$33$330$7190No recorded events in Storm Events since 1996 (data through 2026-06-30).

Total = buildings + agriculture + population equivalence; FEMA values each expected death (or 10 injuries) at $13.7 million (2024 dollars).

NRI risk rating combines expected annual loss with social vulnerability and community resilience; EAL rating rates expected annual loss alone. Both compare this county with all U.S. counties.

Local data needed: state and local landslide and wildfire records (Storm Events records these hazards only in part).

Not applicable to this county per NRI, with no federal declaration and no Storm Events record since 1996: avalanche, coastal flooding, tsunami and volcanic activity. That is the evidence for leaving them out of the plan.

The state hazard mitigation plan also lists hazards for this county; FEMA asks the plan to explain any hazard it leaves out.

Supports FEMA checklist item B1-b: hazard location

Affects the whole county (national data give no location within it): Cold Wave, Drought, Hail, Heat Wave, Ice Storm, Lightning, Strong Wind and Winter Weather.

Inland Flooding: The FEMA Flood Insurance Rate Map (FIRM) is the required location source for flooding. See the FEMA Flood Map Service Center (https://msc.fema.gov) for this county.

Hazards that vary within the county: highest-rated census tracts

Source: 5

HazardHighest-rated census tractsNRI risk rating, score 0 to 100
Earthquaketract 403 (Relatively Low, 44.2); tract 404 (Very Low, 35.2); tract 402 (Very Low, 34.3)
Hurricanetract 402 (Very Low, 36.8); tract 404 (Very Low, 36.3); tract 401 (Very Low, 31.3)
Landslidetract 401 (Relatively Low, 95.5); tract 402 (Relatively Low, 94.9); tract 404 (Relatively Low, 93.4)
Tornadotract 403 (Relatively Moderate, 61.4); tract 404 (Relatively Moderate, 61.1); tract 401 (Relatively Moderate, 60.2)
Wildfiretract 402 (Very Low, 51.7); tract 401 (Very Low, 48.4); tract 404 (Very Low, 45.0)

Up to 3 census tracts per hazard, highest National Risk Index rating first, then highest score; a tract number is the Census tract number (for example 403 is Census Tract 403). FEMA's Resilience Analysis and Planning Tool maps the National Risk Index for every tract: https://www.fema.gov/emergency-managers/practitioners/resilience-analysis-and-planning-tool

Supports FEMA checklist item B1-c: hazard extent

Extent: scale, observed range and worst recorded event per hazard

Sources: 6, 7

HazardScaleRecordscount and yearsObserved rangeWorst recorded eventMost damaging (when different)How it applies to jurisdictionsNote
Cold/Wind Chill, Extreme Cold/Wind Chillwind chill12 records, 1996 to 2019 (12 zone-level)3 days to 31 days (median 3 days); 8 with a recorded value2000-12-01 to 2000-12-31 (4 records, 1 of them a monthly summary record), zone-levelCountywide (zone-level records).
Frost/Freeze (outside NRI's Cold Wave definition)crop damage5 records, 2005 to 2012 (5 zone-level)Frost/Freeze, 2005-05-03, $6,600,000 crop damage (2005 dollars); NWS zone ILZ024Countywide (zone-level records).
DroughtU.S. Drought Monitor scale (D0 to D4)15 records, 2005 to 2013 (15 zone-level)12 days to 290 days (median 22 days); 5 with a recorded value290 days (about 9.5 months), 2005-06-15 to 2006-03-31, a run of 10 consecutive Storm Events drought records, zone-levelDrought, 2005-07-01, property not reported; $12,240,000 crops (zone total, 2005 dollars)Countywide (zone-level records).Storm Events enters a drought at D2 or worse east of the Rockies and D3 or worse from the Rockies west (NWS Instruction 10-1605); NRI drought counts D3 and D4 only.
EarthquakeModified Mercalli (local data)0Storm Events does not record earthquakes; the USGS earthquake catalog is the source.
Hailhail size (inches)96 records, 1959 to 20260.75 in to 2.5 in (median 1 in); 96 with a recorded value2.5 in hail, 1974-06-14; same size also recorded on 1959-09-27Hail, 2003-04-30, $500,000 property; crops not reported (2003 dollars)Event records naming jurisdictions in the plan: Aledo city (8 records), Sherrard village (8 records), Keithsburg city (4 records), Joy village (3 records), Matherville village (3 records), Preemption township (2 records).
Excessive Heat, Heatheat index (in event narratives)5 records, 1997 to 2013 (5 zone-level)1 day to 13 days (median 4 days); 5 with a recorded value13 consecutive days, 1999-07-19 to 1999-07-31, zone-levelCountywide (zone-level records).
Hurricane, Tropical Storm, Tropical DepressionSaffir-Simpson0Storm Events files every zone of a storm's episode under the storm's type; flooding from the storm is filed as Flood or Flash Flood records.
Ice StormSperry-Piltz ice scale (local data)9 records, 2000 to 2024 (9 zone-level)Ice Storm, 2007-02-24, $965,000 property; $0 crops (2007 dollars), 1 direct death (reported for the zone); NWS zone ILZ024Countywide (zone-level records).
Flash Flood, Flood, Lakeshore Flooddamage and flood days (flood depth: FIRM)55 records, 1997 to 2025 (7 zone-level)Flash Flood, 2003-04-30, $10,000,000 property; crops not reported (2003 dollars)Event records naming jurisdictions in the plan: Keithsburg city (14 records), Aledo city (3 records), Preemption township (1 record), Sherrard village (1 record). Zone-level records (7) apply countywide.Flood depth: see the FEMA Flood Insurance Rate Map. Storm Events damage is often $0 or blank for floods, major ones included; FEMA Public Assistance by declaration (B1-d) shows which floods cost the most.
Debris Flownone (count and damage only)0
Lightningannualized frequency (the measure FEMA's Local Mitigation Planning Handbook names)3 records, 1997 to 2006Lightning, 1997-06-05, damage not reported, 1 direct deathLightning, 2006-06-06, $25,000 property; crops not reported (2006 dollars)Event records naming jurisdictions in the plan: Aledo city (1 record), Keithsburg city (1 record), Sherrard village (1 record).Storm Events lists lightning with damage or casualties.
High Wind and Strong Wind (outside NRI's Strong Wind definition)wind speed (kt and mph)8 records, 1996 to 2008 (8 zone-level)43 kt (49 mph) to 53 kt (61 mph) (median 52 kt (60 mph)); 7 with a recorded value53 kt (61 mph), measurement type not recorded, High Wind, 1998-11-09; NWS zone ILZ024High Wind, 1997-04-06, $100,000 property; crops not reported (zone total, 1997 dollars)Countywide (zone-level records).
Thunderstorm Windwind speed (kt and mph)136 records, 1957 to 202650 kt (58 mph) to 78 kt (90 mph) (median 56 kt (64 mph)); 107 with a recorded value78 kt (90 mph) estimated gust, Thunderstorm Wind, 2020-11-10; same speed and measurement basis also recorded on 2006-04-13Thunderstorm Wind, 2003-07-20, $10,000,000 property; $3,000,000 crops (2003 dollars)Event records naming jurisdictions in the plan: Aledo city (24 records), Sherrard village (8 records), Joy village (5 records), Matherville village (5 records), Keithsburg city (4 records), Preemption township (4 records).
TornadoEnhanced Fujita (Fujita before Feb 2007)45 records, 1952 to 2026F/EF0 to F/EF3 (median F/EF1); 43 with a recorded valueF3 tornado, 1974-06-14, 26.9 mi path length (whole path, pre-1996), 440 yd wide, damage not recorded (pre-1996 record), 1 direct injuryTornado, 1973-04-21, $2,500,000 property; crops not recorded (1973 dollars)Event records naming jurisdictions in the plan: Aledo city (5 records), Matherville village (2 records), Preemption township (2 records), Joy village (1 record).Before 1996 a tornado is listed once, under the county where it began, with its whole path's rating and length; from 1996 on, each county lists its own segment. Length is not used to rank tornadoes (see Methods).
Wildfireacres burned (local data)0
Winter Storm, Heavy Snow, Blizzard, Lake-Effect Snow, Winter Weather, Sleetnone in data (snowfall: local data)124 records, 1996 to 2026 (124 zone-level)Winter Weather, 2006-03-21, $2,000 property; crops not reported (2006 dollars); NWS zone ILZ024Countywide (zone-level records).

In event narratives only (local data needed): wind chill, temperature, heat index, ice thickness, acres burned and snow depth; any physical measure of debris flow and lightning.

Storm Events records are more complete after 1996; before 1996 only Tornado (from 1950), Hail and Thunderstorm Wind (from 1955) exist. Zone-level records from zones that no NWS zone-county file places in this county (mostly before 2020) are not counted here (the Methods page explains the zone matching).

Dollars are nominal (as reported), labeled with the year; not adjusted for inflation.

A monthly summary record covers most or all of a month; it does not count days at wave conditions.

Supports FEMA checklist item B1-d: previous occurrences

Federal declarations for this county: 15 declarations covering 12 separate hazard incidents counted in this packet (declarations for the same incident count once; non-natural and evacuation-only declarations are not counted).

Federal disaster declarations for this county

Sources: 1, 2, 3

DeclaredIncident beganFEMA numberTypeTitleMapped hazardCounty Public Assistancefederal share obligated, nominal dollarsNotes
2020-03-262020-01-20DR-4489-ILMajor disasterCOVID-19 PandemicNon-natural, not counted$57,099.02
2020-03-132020-01-20EM-3435-ILEmergencyCOVID-19Non-natural, not countedno Public Assistance recordedsame incident as DR-4489
2019-09-192019-02-24DR-4461-ILMajor disasterSevere Storms and FloodingInland Flooding$2,337,578.31
2013-05-102013-04-16DR-4116-ILMajor disasterSevere Storms, Straight-Line Winds, and FloodingInland Flooding (primary); also designated: Strong Wind$849,893.39
2011-03-172011-01-31DR-1960-ILMajor disasterSevere Winter Storm and SnowstormWinter Weather$80,217.15
2008-06-242008-06-01DR-1771-ILMajor disasterSevere Storms and FloodingInland Flooding$2,817,467.20
2005-09-072005-08-29EM-3230-ILEmergencyHurricane Katrina EvacuationHurricane: evacuation support, not a local hazard event; not countedno Public Assistance recorded
2001-05-092001-04-18DR-1368-ILMajor disasterFloodingInland Flooding$788,113.05
1999-01-081999-01-01EM-3134-ILEmergencyIl-Winter Storm 1/1/99Winter Weather$86,883.88
1993-07-091993-04-13DR-997-ILMajor disasterSevere Storms & FloodingInland Floodingno Public Assistance recorded
1979-01-161979-01-16EM-3068-ILEmergencyBlizzards & SnowstormsWinter Weatherno Public Assistance recorded
1974-06-101974-06-10DR-438-ILMajor disasterSevere Storms & FloodingInland Floodingno Public Assistance recorded
1973-04-261973-04-26DR-373-ILMajor disasterSevere Storms & FloodingInland Floodingno Public Assistance recorded
1969-06-061969-06-06DR-262-ILMajor disasterFloodingInland Floodingno Public Assistance recorded
1965-04-251965-04-25DR-194-ILMajor disasterTornadoes, Severe Storms & FloodingTornado (primary); also designated: Inland Floodingno Public Assistance recorded

County Public Assistance: applicants the FEMA record places in this county, including any state agencies FEMA files there; statewide rows are listed on the state page; federal share obligated, nominal dollars.

Statewide declarations

Source: 2

DeclaredIncident beganFEMA numberTypeTitleMapped hazard
1961-05-271961-05-27DR-115-ILMajor disasterFloods & TornadoesInland Flooding (primary); also designated: Tornado
1957-06-221957-06-22DR-78-ILMajor disasterFloodsInland Flooding

FEMA recorded these with designated area Statewide and no county, so they are listed on every county page in the state and not counted with county rows. Local data needed: whether each one affected this county.

Public Assistance not placed in any Illinois county: 1 row, $797,909.42; listed on the Illinois state page.

Source: 3

Previous occurrences by hazard, with explicit no-event rows

Sources: 2, 6, 7

HazardStorm Events records, all years on file(years in the Period column)Since plan approvalrecordsIn the 12 months before plan approvalrecordsLast 5 yearsrecordsDeclared incidents, all yearsseparate disastersDeclared since approvalseparate disastersPeriodStatement
Cold Wave17000001996 to 2026-06-30Includes 5 Frost/Freeze records.
Drought15000001996 to 2026-06-30
Earthquake000000Storm Events does not record earthquakes; the USGS earthquake catalog is the source.
Hail9631015001955 to 2026-06-30
Heat Wave5000001996 to 2026-06-30
Hurricane0000001996 to 2026-06-30No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Ice Storm9101001996 to 2026-06-30
Inland Flooding55304901996 to 2026-06-30
Landslide0000001996 to 2026-06-30No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Lightning3000001996 to 2026-06-30
Strong Wind14410321101955 to 2026-06-30Includes 7 High Wind and 1 Strong Wind records.
Tornado45608101950 to 2026-06-30
Wildfire0000001996 to 2026-06-30No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Winter Weather124226301996 to 2026-06-30

Notable Storm Events records

Sources: 1, 6, 7

DateEvent typeMagnitude or extentDamagenominal dollarsDeaths, injuriesdirect onlyLocationWhy listed
2020-11-10Thunderstorm Wind78 kt (90 mph) estimated gustdamage not reported0, 0JOYB1-c worst recorded: Thunderstorm Wind
2007-02-24Ice Storm$965,000 property; $0 crops (zone total, 2007 dollars)1, 0NWS zone ILZ024 (MERCER), zone-leveldeaths or injuries recorded
2005-06-15Droughtdamage not reported0, 0NWS zone ILZ024 (MERCER), zone-levelB1-c worst recorded: Drought
2005-05-03Frost/Freezeproperty not reported; $6,600,000 crops (zone total, 2005 dollars)0, 0NWS zone ILZ024 (MERCER), zone-levelB1-c worst recorded: Frost/Freeze
2003-04-30Flash Flood$10,000,000 property; crops not reported (2003 dollars)0, 0COUNTYWIDEB1-c worst recorded: Flash Flood, Flood, Lakeshore Flood
2000-12-01Cold/Wind Chilldamage not reported0, 0NWS zone ILZ024 (MERCER), zone-levelB1-c worst recorded: Cold/Wind Chill, Extreme Cold/Wind Chill
1999-07-19Heatdamage not reported0, 0NWS zone ILZ024 (MERCER), zone-levelB1-c worst recorded: Excessive Heat, Heat
1998-11-09High Wind53 kt (61 mph), measurement type not recordeddamage not reported0, 0NWS zone ILZ024 (MERCER), zone-levelB1-c worst recorded: High Wind and Strong Wind
1997-06-05Lightningdamage not reported1, 0ALEDOdeaths or injuries recorded
1991-11-29Thunderstorm Windspeed not recordeddamage not recorded (pre-1996 record)0, 3location not recordeddeaths or injuries recorded
1974-06-14Hail2.5 indamage not recorded (pre-1996 record)0, 0location not recordedB1-c worst recorded: Hail
1974-06-14TornadoF3, 26.9 mi path length (whole path, pre-1996), 440 yd widedamage not recorded (pre-1996 record)0, 1location not recordedB1-c worst recorded: Tornado

The full list is in the Excel file, sheet "B1-d Storm Events history" (513 rows).

Location is the place NOAA recorded, as written in its data; it need not be a jurisdiction in this plan.

Local data needed: state-declared emergencies, from your state emergency management agency (federal data do not include them).

FEMA's declaration data list no tribal or special-area declarations for this state.

Supports FEMA checklist item B1-e: probability of future events

Probability: FEMA annualized frequency and descriptor per hazard

Sources: 5, 6

HazardFEMA annualized frequency (modeled)unit per rowUnitIn plain termsDescriptorDescriptor basisNRI events or days in its record period (hail, wind and tornado are area-weighted, so can be fractional)NRI periodLocationNote
Cold Wave5.37event-days per yearabout 5.37 days per yearLikelyStorm Events event-days in 7 of 30 years, 1996 to 2025 (23.3%)1022005-11-12 to 2024-11-12 (19 years)countywide
Drought8.21event-days per yearabout 8.21 days per yearLikelyStorm Events event-days in 4 of 30 years, 1996 to 2025 (13.3%)2172000 to 2025 (25.25 years; D3 and D4 only)countywide
Earthquake0.00117annual probability at a locationchance a given location in the county has at least minor-damage shaking in a year: 0.117%not shownmodeledsee B1-fNo descriptor (Storm Events does not record earthquakes).
Hail4.23events per yearabout 4.23 per yearHighly likelyFEMA annualized frequency (modeled)160.7 (modeled)1986 to 2023 (38 years)countywide
Heat Wave8.16event-days per yearabout 8.16 days per yearLikelyStorm Events event-days in 5 of 30 years, 1996 to 2025 (16.7%)1232005-11-12 to 2024-11-12 (19 years)countywide
Hurricane0.01events per yearabout 1 in 100 yearsPossibleFEMA annualized frequency (modeled)01851 to 2024 (Atlantic)see B1-fNRI counts hurricane and tropical storm tracks passing within storm-force wind range; federal declarations are in B1-d.
Ice Storm0.668event-days per yearabout 0.668 days per yearLikelyStorm Events event-days in 7 of 30 years, 1996 to 2025 (23.3%)451946-12-31 to 2014-02-12 (67 years)countywide
Inland Flooding1.64event-days per yearabout 1.64 days per yearLikelyStorm Events event-days in 20 of 30 years, 1996 to 2025 (66.7%)461996 to 2023 (28 years)see B1-f
Landslide0.239events per year (modeled)about 1 in 4 yearsLikelyFEMA annualized frequency (modeled)not shownmodeledsee B1-f
Lightning44.8days per year with a strikeabout 44.8 days per yearHighly likelyFEMA annualized frequency (modeled)not shown1995 to 2023 (29 years; CONUS)countywide
Strong Wind6.25events per yearabout 6.25 per yearHighly likelyFEMA annualized frequency (modeled)2381986 to 2023 (38 years)countywide
Tornado0.532events per yearabout 0.53 per yearLikelyFEMA annualized frequency (modeled)not shown1950 to 2023 (EF2+); 1986 to 2023 (EF0-1)see B1-f
Wildfire0.000297annual probability at a locationchance a given location in the county burns in a year: 0.0297%Storm Events records in 0 of 30 years, 1996 to 2025 (0%)not shownmodeledsee B1-fNo descriptor: no Storm Events record 1996 to 2025
Winter Weather14.2event-days per yearabout 14.2 days per yearHighly likelyStorm Events event-days in 28 of 30 years, 1996 to 2025 (93.3%)2692005-11-12 to 2024-11-12 (19 years)countywide

FEMA annualized frequency (modeled) is the National Risk Index v1.20 (December 2025) estimate of how often a hazard affects this county in a year; it is not recorded events divided by years, and its unit differs by hazard (events, event-days, or days with a lightning strike per year). For earthquake, wildfire, coastal flooding and tsunami the value is the chance (or number of events) at a location in the county, not across the county, so no "1 in N years" is given and the descriptor comes from Storm Events where it has a record (none for earthquake). The Methods page gives each hazard's method, from FEMA's National Risk Index Technical Documentation v1.20.

Where NRI gives event-days, the descriptor comes from the share of years with a Storm Events record; NRI's source records more events, so the two differ.

Descriptor scale used in this packet (defined per unit)

Sources: 5, 6

UnitDescriptorDefinition
events per yearHighly likely1 or more per year
events per yearLikelyabout once in 1 to 10 years
events per yearPossibleabout once in 10 to 100 years
events per yearUnlikelyless than once in 100 years
annual probabilityLikely10% to under 100% chance in a given year
annual probabilityPossible1% to under 10% chance in a given year
annual probabilityUnlikelyunder 1% chance in a given year
event-days (share of years)Highly likelyevent-days recorded in 90% or more of years
event-days (share of years)Likelyevent-days recorded in 10% to under 90% of years
event-days (share of years)Possibleevent-days recorded in some years but under 10% of years
lightning strike-daysHighly likelycloud-to-ground strikes on 1 or more days per year

Intensity bands: historical frequency (Storm Events)

Source: 6

HazardBandYearsEventscounty-coded recordsYears in periodEvents per yearevents / years
Hail1.00-1.99 in1996 to 202540301.33
Hail2.00 in+1996 to 20251300.0333
Thunderstorm Wind (counted as NRI Strong Wind)50-64 kt1996 to 202583302.77
Thunderstorm Wind (counted as NRI Strong Wind)65 kt+1996 to 202512300.4
Thunderstorm Wind (counted as NRI Strong Wind)unmeasured or below 50 kt1996 to 20253300.1
TornadoEF0-11996 to 202529300.967
TornadoEF2-31996 to 20253300.1
TornadoEF4-51996 to 20250300
Tornadounrated (EFU)1996 to 20252300.0667

The bands show how often events of each severity were recorded in this county, to profile how severe events have been (FEMA's probability item asks for the range of intensities).

Hail smaller than 1 inch is not counted: on 2010-01-05 the National Weather Service raised its severe-hail threshold from 3/4 inch to 1 inch, so smaller reports became less common after 2009 (NWS Service Change Notice 09-52). NRI hail frequency uses a 0.75 inch threshold.

Optional: future conditions. Not a required item in the 2025 FEMA Local Mitigation Planning Policy Guide; some states ask for it. The federal Climate Mapping for Resilience and Adaptation (CMRA) site gives county exposure to future climate conditions (https://resilience.climate.gov/).

Supports FEMA checklist item B1-f: hazards that vary across jurisdictions

Range of census tract risk within the county

Source: 5

HazardTractsrated of allNRI risk score, 0 to 100Tracts by rating
MinMedianMax
Cold Wave4 of 468.381.485.5Relatively High 2, Relatively Moderate 2
Drought4 of 491.297.298.3Relatively High 2, Relatively Moderate 1, Relatively Low 1
Earthquake4 of 430.634.844.2Relatively Low 1, Very Low 3
Hail4 of 478.780.482.6Relatively Moderate 4
Heat Wave4 of 483.084.385.2Relatively High 2, Relatively Moderate 2
Hurricane4 of 423.533.836.8Very Low 4
Ice Storm4 of 494.895.295.4Relatively High 4
Inland Flooding4 of 421.122.968.6Relatively Moderate 1, Relatively Low 3
Landslide4 of 478.994.295.5Relatively Low 3, Very Low 1
Lightning4 of 498.598.798.8Very High 4
Strong Wind4 of 497.998.699.1Very High 4
Tornado4 of 458.960.661.4Relatively Moderate 4
Wildfire4 of 427.146.751.7Very Low 4
Winter Weather4 of 479.580.381.0Relatively High 4

Cold Wave: Agriculture is 51% of NRI's expected annual loss for this hazard in the county, so the tract range mostly reflects where crop and livestock value is.

Drought: Agriculture is all of NRI's expected annual loss for this hazard in the county, so the tract range mostly reflects where crop and livestock value is.

Rated tracts only: No Rating (score 0.0), Not Applicable and Insufficient Data tracts are counted but not used for the minimum, median and maximum.

The score ranks a tract against all U.S. tracts (100 = highest). The rating is FEMA's category for the tract's risk value, computed differently, so the two can disagree.

Frequency data for cold wave, drought, hail, heat wave, ice storm, lightning, strong wind and winter weather are county-wide or coarse (49 km grid or NWS zone), the same for every jurisdiction; the tract range mostly reflects where buildings and people are (crop and livestock value where a line above names agriculture).

Each jurisdiction (starting figures from federal data)

Sources: 1, 3, 4, 6

JurisdictionTypePlan statusRepetitive lossFMA RL and SRL (44 CFR 77.2); repeat-flood, any definitionPublic Assistance to this jurisdictionFEMA records matched by applicant name; federal share obligated, nominal dollarsEvent records naming this placeall years; since its planNotes
Mercer CountyCountyApproved, expires 2029-06-03FMA RL 0, SRL 0; any 0$590,718.360 total; 0 since its plan
Aledo cityCityApproved, expires 2029-06-03FMA RL 0, SRL 0; any 0no Public Assistance recorded41 total; 1 since its plan
Joy villageVillageApproved, expires 2029-06-03FMA RL 0, SRL 0; any 0$6,826.079 total; 0 since its plan
Keithsburg cityCityApproved, expires 2029-06-03FMA RL 0, SRL 1; any 3$384,658.2723 total; 3 since its plan
Matherville villageVillageApproved, expires 2029-06-03FMA RL 0, SRL 0; any 0no Public Assistance recorded10 total; 0 since its plan
Sherrard villageVillageApproved, expires 2029-06-03FMA RL 0, SRL 0; any 0no Public Assistance recorded18 total; 3 since its plan
Abington townshipTownshipApproved, expires 2029-06-03$40,042.100 total; 0 since its planNo NFIP community ID on this jurisdiction's plan row.
Preemption townshipTownshipApproved, expires 2029-06-03$273,376.979 total; 2 since its planNo NFIP community ID on this jurisdiction's plan row.

Repetitive-loss counts are for whole NFIP communities, which can extend beyond this county (see the note in B2-c).

School districts and special districts get a plan clock row only.

County Public Assistance in B1-d also includes applicants filed under the county that are not jurisdictions in this plan (for example state agencies, special districts and nonprofits), so the jurisdiction rows add up to less.

Supports FEMA checklist items B2-a and B2-b: vulnerability and potential impacts

Local data needed

The table below gives county-level starting figures; the plan describes impacts for each jurisdiction and its own assets.

  • Critical facilities and lifelines per hazard
  • A problem statement per jurisdiction per hazard
  • Changes in development in hazard-prone areas since the last approval, or a statement of none (E1-a)
  • Future assets

County-level starter: exposure, expected annual loss and damage since the plan

Sources: 1, 2, 3, 5, 6, 7

HazardBuilding exposuremodeled dollarsAgriculture exposuremodeled dollarsPopulation exposedpeopleEAL buildingsmodeled dollars per yearEAL agriculturemodeled dollars per yearCost of expected deaths and injuriesFEMA's dollar value per year, not property damageEAL as % of exposurebuildings; agriculture where notedStorm Events damage since 2024-06-04county-coded records, property plus crops, nominal dollarsZone-level damage since planproperty plus crops, reported for the zonePublic Assistance since plannominal dollars; see noteNote
Cold Wave$1,646,788,321$280,128,67615,683$83$397,852$378,773under 0.0001%
Droughtn/a$190,865,253n/an/a$907,319n/a0.475% (agriculture)NRI has no building exposure for this hazard; agriculture shown
Earthquake$2,558,063,233n/a15,699$35,756n/a$32,8510.0014%
Hail$1,646,788,667$280,128,67615,683$155,285$5,723$21,2080.00943%$0
Heat Wave$1,646,788,321$280,128,67615,683$3$7$551,210under 0.0001%
Hurricane$1,646,788,667$280,128,67615,683$318$3,446under $1under 0.0001%
Ice Storm$1,628,513,195n/a15,507$42,722n/a$242,4930.00262%$0
Inland Flooding$1,645,203,553$26,207,625191$1,728,957$211,651$9,879n/a (see note)$0NRI counts the full building value of any census block with some flood loss; this is not the value of buildings in the floodplain. Use local FIRM overlays for B2-a/B2-b.
Landslide$28,189,367n/a293$106n/a$7,6190.000377%
Lightning$1,646,788,667n/a15,683$2,632n/a$489,2860.00016%
Strong Wind$1,646,788,667$280,128,67615,683$428,009$376,079$405,0280.026%$0
Tornado$1,646,788,667$280,128,67615,683$128,935$1,456$336,9630.00783%$0
Wildfire$16,420,069$14,985,300620$356$33$3300.00217%
Winter Weather$1,646,788,321$280,128,67615,683$507$1,306$38,494under 0.0001%$0

Totals since 2024-06-04 (Storm Events through 2026-06-30): 22 county-coded records, 19 with a damage value recorded (including $0), $0; 3 zone-level records, 3 with a damage value recorded (including $0), $0 reported for the zone; Public Assistance: no counted declaration since the plan.

FEMA does not split Public Assistance by hazard. A declaration mapped to several hazards is listed under each of them with its full amount, so the per-hazard column does not add up to the total; the unit total counts each declaration once.

NRI computes earthquake exposure on its own basis, so it exceeds the county building value in B2-a.

Supports FEMA checklist item B2-a: vulnerability (county context)

County context

Source: 5

MeasureValue
Population15,683
Building value (total, not at risk)$1,646,788,667
Agriculture value (total, not at risk)$280,128,676
NRI risk rating (all hazards)Very Low
Expected annual loss, buildings and agriculture, all hazards$4,428,540
Expected annual loss, population equivalence, all hazards (NRI values each statistical life at $13.7M; a modeled value of expected deaths and injuries, not property damage)$2,514,133
Social vulnerability ratingVery Low
Community resilience ratingVery High
NRI versionDecember 2025

FEMA's all-hazard expected annual loss adds buildings, agriculture and population equivalence; this table gives the property part and the population-equivalence part as separate rows.

Social vulnerability: higher means people are more likely to be harmed and slower to recover. Community resilience: lower means the community is less able to recover. High social vulnerability and low resilience both raise the NRI risk rating.

Supports FEMA checklist item B2-c: repetitive loss properties

Repetitive loss in this county, both definitions

Sources: 1, 4

DefinitionPropertiesSevere repetitive lossProperties
Repetitive loss, FMA definition (44 CFR 77.2)0Severe repetitive loss, FMA definition (44 CFR 77.2)1
Repetitive loss, NFIP insurance definition3Severe repetitive loss, NFIP insurance definition1

The state NFIP coordinator's list, the source FEMA's Handbook names, often uses the NFIP insurance definition (second row).

Repeat-flood properties: county and state-level rows

Sources: 1, 4

ScopeRL, FMApropertiesSRL, FMApropertiesRL, NFIPpropertiesSRL, NFIPpropertiesAny categorypropertiesMitigatedpropertiesCurrently insuredproperties
County total0131300
of which: Keithsburg city0131300
Statewide, no county in FEMA's file0050500

The statewide row counts properties FEMA's file gives with no county in this state; they are listed for reference and are not in this county's counts.

Repeat-flood properties by jurisdiction in the plan (NFIP community)

Sources: 1, 4

JurisdictionNFIP community IDRL, FMApropertiesSRL, FMApropertiesRL, NFIPpropertiesSRL, NFIPpropertiesAny categorypropertiesMitigatedpropertiesCurrently insuredproperties
Mercer County1708060000000
Aledo city1705070000000
Joy village1712590000000
Keithsburg city1705080131300
Matherville village1708330000000
Sherrard village1712620000000

Counts by occupancy group for each jurisdiction are in the Excel file, sheet "B2-c Jurisdictions".

Jurisdiction rows are whole NFIP communities and need not add up to the county total: a community that extends into another county is counted in full on each jurisdiction row, while the county table counts only its part in this county.

County repeat-flood properties by occupancy group

Sources: 1, 4

Occupancy groupRL, FMApropertiesSRL, FMApropertiesRL, NFIPpropertiesSRL, NFIPpropertiesAny categorypropertiesMitigatedpropertiesCurrently insuredproperties
single-family residential0000000
2 to 4 unit residential0000000
other residential0111100
non-residential0020200
not reported0000000

FEMA's occupancy groups have no institutional class; institutional properties are counted in non-residential or other residential in the table by occupancy group.

FMA RL and FMA SRL are the Flood Mitigation Assistance definitions (44 CFR 77.2), the ones the FEMA Local Mitigation Planning Policy Guide cites. NFIP repetitive loss (the FEMA insurance definition) is 2 or more claims over $1,000 in 10 years, and a property can leave that group once it is mitigated. Also shown: NFIP severe repetitive loss, any category, mitigated and currently insured. The Methods page gives the OpenFEMA field details.

Counts are aggregates of FEMA's public NFIP Multiple Loss Properties file (FEMA's data date 2026-08-02; file version 2026-08-04). No property is identified. County assignment is FEMA's geocode.

In this county 0 properties are FMA repetitive loss but not NFIP repetitive loss, and 3 properties are NFIP repetitive loss but not FMA repetitive loss.

Exact counts; no count suppression.

Sources

Tables cite these sources by number. The full list, for the plan's bibliography (FEMA review item A4-a):

  1. FEMA, OpenFEMA HazardMitigationPlanStatuses v1, version 2026-09-29T134039Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/HazardMitigationPlanStatuses (API)
  2. FEMA, OpenFEMA DisasterDeclarationsSummaries v2, version 2026-09-29T162832Z, pulled 2026-09-30, https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries (API)
  3. FEMA, OpenFEMA PublicAssistanceFundedProjectsSummaries v1, version 2026-09-29T150754Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/PublicAssistanceFundedProjectsSummaries (API)
  4. FEMA, OpenFEMA NfipMultipleLossProperties v1, version 2026-08-04T164045Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/NfipMultipleLossProperties (API)
  5. FEMA, FEMA National Risk Index 1.20.0 (December 2025), county and census tract tables, version 1.20.0, pulled 2026-09-30, https://www.fema.gov/about/reports-and-data/openfema/nri/v120/NRI_Table_Counties.zip (download, 25 MB), https://www.fema.gov/about/reports-and-data/openfema/nri/v120/NRI_Table_CensusTracts.zip (download, 635 MB)
  6. NOAA NCEI, NOAA NCEI Storm Events Database, details files (csvfiles v1.0), version c20260918, pulled 2026-09-30, https://www.ncei.noaa.gov/pub/data/swdi/stormevents/csvfiles/
  7. NOAA National Weather Service, NWS county-public forecast zones correlation file, version bp03mr20 to bp16ap26 (11 files; newest bp16ap26), pulled 2026-09-30, https://www.weather.gov/gis/ZoneCounty
  8. U.S. Census Bureau, Census 2024 Gazetteer, 2020 place by county, CT county-to-cousub crosswalk, version 2024-gazetteer, pulled 2026-09-30, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_counties_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_cousubs_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_place_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_unsd_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_elsd_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_scsd_national.zip, https://www2.census.gov/geo/docs/reference/codes2020/national_place_by_county2020.txt, https://www2.census.gov/geo/docs/reference/ct_change/ct_cou_to_cousub_crosswalk.xlsx (used to match place names and codes; no table prints its values)

What this packet is and what the plan adds

This packet is the federal data for the plan's risk assessment (the summary on page 1 says how it is organized); the plan and FEMA's review decide whether each item is met.

The plan adds what only the community has: local data on assets, critical facilities, development and each jurisdiction's impacts; local hazard history, including state-declared emergencies; the mitigation strategy; and adoption.

How the federal data are built: National Risk Index values are FEMA's model, not counts of events. Storm Events is more complete from 1996; zone-level records are placed by forecast zone, not by location in the county. Public Assistance for a jurisdiction is matched by applicant name. The Methods page gives every rule and the known edge cases.

OpenFEMA disclaimer

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

Reuse, citation and corrections

Reuse and citation: Hazard Plain text and tables are licensed under Creative Commons Attribution 4.0 International (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); credit Hazard Plain and the release. The underlying federal data are public domain; OpenFEMA data are also subject to the OpenFEMA terms and conditions.

Cite this: Hazard Plain (2026). Mercer County, IL: risk-assessment baseline packet, release 2026-10 (data as of 2026-09-30; County FIPS 17131). Automated baseline. https://hazardplain.org/il/17131/ Built from FEMA OpenFEMA, the FEMA National Risk Index and NOAA NCEI Storm Events; source versions in the packet's Sources list.

Corrections: to report an error, name the packet, the table and what your records show. Contact: contact@hazardplain.org