Boise County, ID: risk-assessment baseline packet, release 2026-10

Summary

Plan status as of 2026-09-30: Approved, expires 2031-05-26. Plan: Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978), approved 2026-05-27.

Since the plan was approved on 2026-05-27: no new federal declaration.

NOAA Storm Events records since that date: 0 records (data through 2026-06-30).

Highest expected annual loss (FEMA National Risk Index, modeled total; see B1-a): Wildfire ($8,240,645 a year), Inland Flooding ($5,509,493) and Avalanche ($1,370,004).

Repetitive-loss flood properties now: FMA RL 0, SRL 0 (44 CFR 77.2); any definition: 0.

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.

Terms used

EAL:: expected annual loss: FEMA's modeled average yearly loss from a hazard.
NRI:: FEMA's National Risk Index (version 1.20, December 2025).
NFIP:: National Flood Insurance Program.
RL, SRL:: repetitive loss and severe repetitive loss: flood-insured properties with repeated claims (definitions in B2-c).
FMA, HMGP:: Flood Mitigation Assistance and Hazard Mitigation Grant Program, FEMA mitigation grants.
PA:: FEMA Public Assistance: disaster aid to governments and some nonprofits.
Zone-level:: NOAA logged the event for a National Weather Service forecast zone, which may include parts of neighboring counties.
County-coded:: NOAA logged the event to this county.
FIPS:: the federal code for a place; 16015 is this area.
D0 to D4:: U.S. Drought Monitor categories, from abnormally dry (D0) to exceptional drought (D4).
F/EF, EFU:: Fujita and Enhanced Fujita tornado ratings; EFU is an unrated tornado.
kt, CONUS:: knots (1 kt is about 1.15 mph); the contiguous United States.
CFR:: Code of Federal Regulations.
A4-a, E1-a:: other items of FEMA's Local Mitigation Plan Review Tool (sources, and changes since the last plan).
Dollars:: nominal (as reported, labeled with the year), not adjusted for inflation.

Plan clock

Status:: Approved, expires 2031-05-26
Plan:: Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978)
Approved:: 2026-05-27
Days to expiry:: 1,699

What changed since your last plan (approved 2026-05-27)

New federal declarations:: none
Storm Events records since approval:: 0 records (data through 2026-06-30)
Repetitive loss now:: FMA RL 0, SRL 0 (44 CFR 77.2); any definition: 0
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

Source: 1

Jurisdiction	Type	Status	Plan	Approved	Expires	Days to expirynegative = days since expiry	Update underway	Notes
Boise County	County	Approved, expires 2031-05-26	Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978)	2026-05-27	2031-05-26	1,699
Crouch city	City	Plan 109978 approved 2026-05-27, pending adoption here; not yet eligible	Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978), pending adoption here	2026-05-27 by FEMA; not yet adopted here	2031-05-26 once adopted		FEMA tracker shows a plan approvable pending adoption	Not yet eligible: adopt the approved plan.
Horseshoe Bend city	City	Approved, expires 2031-05-26	Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978)	2026-05-27	2031-05-26	1,699
Idaho City city	City	Approved, expires 2031-05-26	Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978)	2026-05-27	2031-05-26	1,699
Placerville city	City	Plan 109978 approved 2026-05-27, pending adoption here; not yet eligible	Boise County Multi-Jurisdiction Hazard Mitigation Plan (FEMA plan 109978), pending adoption here	2026-05-27 by FEMA; not yet adopted here	2031-05-26 once adopted		FEMA tracker shows a plan approvable pending adoption	Not yet eligible: adopt the approved plan.
Emmett Independent School District 221	School/School District	Expired on 2024-09-09	Gem County (FEMA plan 105727)	2019-09-09	2024-09-09	-751	FEMA tracker shows a plan in progress

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

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 EAL	Hazard	NRI risk rating	EAL rating	EAL buildingsmodeled dollars per year	EAL agriculturemodeled dollars per year	Cost of expected deaths and injuriesFEMA's dollar value per year, not property damage	EAL total (see note)modeled dollars per year	Storm Events records, 1996 to 2026-06-30count	Why this hazard can be left outNRI Not Applicable, no declaration and no Storm Events record since 1996	Storm Events coverage note
1	Wildfire	Relatively Moderate	Relatively High	$7,908,596	$88	$331,961	$8,240,645	1
2	Inland Flooding	Relatively Low	Relatively Low	$5,506,880	$151	$2,461	$5,509,493	27
3	Avalanche	Relatively High	Relatively Moderate	$4	n/a	$1,370,000	$1,370,004	1
4	Landslide	Relatively Moderate	Relatively Moderate	$27,256	n/a	$328,733	$355,989	5
5	Strong Wind	Relatively Low	Relatively Low	$4,009	$9	$220,618	$224,636	31		Includes 9 High Wind and 2 Strong Wind records (NOAA non-thunderstorm wind types, outside NRI's Strong Wind definition).
6	Earthquake	Very Low	Very Low	$142,358	n/a	$15,926	$158,284			Storm Events does not record earthquakes.
7	Winter Weather	Relatively Low	Relatively Low	$180	$44	$70,192	$70,416	133
8	Heat Wave	Very Low	Very Low	$12	$141	$36,107	$36,261	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
9	Lightning	Very Low	Very Low	$1,625	n/a	$30,061	$31,686	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
10	Tornado	Very Low	Very Low	$7,926	$16	$5,190	$13,132	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
11	Cold Wave	Very Low	Very Low	$50	$103	$12,775	$12,928	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
12	Hail	Very Low	Very Low	$9,152	$200	$1,246	$10,597	13
13	Ice Storm	Very Low	Very Low	$413	n/a	$7,338	$7,751	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
14	Volcanic Activity	Very Low	Very Low	under $1	n/a	$3	$3	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
15	Drought	Very Low	Very Low	n/a	$1	n/a	$1	0		No recorded events in Storm Events since 1996 (data through 2026-06-30).
	Hurricane	Not Applicable	Not Applicable					0	NRI rates hurricane Not Applicable for this county, and no counted federal declaration for this county names it (EM-3244-ID names it but is not counted as a local occurrence; see B1-d).	No 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 lightning and volcanic activity 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: coastal flooding and tsunami. 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

Hazard	Highest-rated census tractsNRI risk rating, score 0 to 100
Avalanche	tract 9502.01 (Relatively Moderate, 85.2); tract 9502.03 (Relatively Moderate, 83.9); tract 9502.02 (Relatively Moderate, 83.5)
Earthquake	tract 9502.02 (Relatively Low, 74.7); tract 9502.03 (Relatively Low, 60.6); tract 9502.01 (Very Low, 28.1)
Hurricane	no tract has a National Risk Index rating for this hazard
Landslide	tract 9502.02 (Relatively High, 99.7); tract 9502.03 (Relatively High, 99.6); tract 9502.01 (Relatively High, 99.6)
Tornado	tract 9502.03 (Very Low, 16.0); tract 9502.02 (Very Low, 10.0); tract 9502.01 (Very Low, 9.4)
Volcanic Activity	tract 9502.03 (Very Low, 69.0); tract 9502.01 (Very Low, 66.1); tract 9502.02 (Very Low, 47.6)
Wildfire	tract 9502.01 (Very High, 99.8); tract 9502.03 (Very High, 99.8); tract 9502.02 (Very High, 99.5)

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 9502.01 is Census Tract 9502.01). 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

Hazard	Scale	Recordscount and years	Observed range	Worst recorded event	Most damaging (when different)	How it applies to jurisdictions	Note
Avalanche	none (count and damage only)	1 record, 2010 (1 zone-level)		No damage reported in 1 record.		Countywide (zone-level records).	Physical measure: in event narratives only (local data needed).
Cold/Wind Chill, Extreme Cold/Wind Chill	wind chill	0					Wind chill: in event narratives only (local data needed).
Frost/Freeze (outside NRI's Cold Wave definition)	crop damage	0					Temperature: in event narratives only (local data needed).
Drought	U.S. Drought Monitor scale (D0 to D4)	0					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.
Earthquake	Modified Mercalli (local data)	0					Storm Events does not record earthquakes; the USGS earthquake catalog is the source.
Hail	hail size (inches)	21 records, 1961 to 2024	0.75 in to 2 in (median 1 in); 21 with a recorded value	2 in hail, 1961-07-05		Event records naming jurisdictions in the plan: Horseshoe Bend city (5 records), Crouch city (2 records), Placerville city (2 records).
Excessive Heat, Heat	heat index (in event narratives)	0					Heat index: in event narratives only (local data needed).
Hurricane, Tropical Storm, Tropical Depression	Saffir-Simpson	0					Storm 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 Storm	Sperry-Piltz ice scale (local data)	0					Ice thickness: in event narratives only (local data needed).
Flash Flood, Flood, Lakeshore Flood	damage and flood days (flood depth: FIRM)	27 records, 1997 to 2025 (1 zone-level)		Flood, 2014-08-06, $0 property; $8,000,000 crops (2014 dollars) (as recorded; larger than this county's annual agriculture value in the National Risk Index (the county or state extension service keeps crop loss records))		Event records naming jurisdictions in the plan: Idaho City city (6 records), Horseshoe Bend city (4 records). Zone-level records (1) 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 Flow	none (count and damage only)	5 records, 1997 to 2024		No damage reported in 5 records.		Event records naming jurisdictions in the plan: Idaho City city (1 record).	Physical measure: in event narratives only (local data needed).
Lightning	annualized frequency (the measure FEMA's Local Mitigation Planning Handbook names)	0					Storm Events lists lightning with damage or casualties; physical measure in event narratives only (local data needed).
High Wind and Strong Wind (outside NRI's Strong Wind definition)	wind speed (kt and mph)	11 records, 2006 to 2025 (11 zone-level)	43 kt (49 mph) to 61 kt (70 mph) (median 50 kt (58 mph)); 11 with a recorded value	61 kt (70 mph) estimated gust, High Wind, 2025-12-17; NWS zone IDZ013	Strong Wind, 2013-05-21, $10,000 property; $0 crops, reported for the zone (2013 dollars)	Countywide (zone-level records).
Thunderstorm Wind	wind speed (kt and mph)	27 records, 1970 to 2025	48 kt (55 mph) to 78 kt (90 mph) (median 52.5 kt (60 mph)); 20 with a recorded value	78 kt (90 mph) measured gust, Thunderstorm Wind, 2008-07-22	Thunderstorm Wind, 1993-05-03, $50,000 property; crops not recorded (1993 dollars)	Event records naming jurisdictions in the plan: Horseshoe Bend city (5 records), Idaho City city (3 records), Placerville city (2 records).
Tornado	Enhanced Fujita (Fujita before Feb 2007)	0					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).
Volcanic Ash, Volcanic Ashfall	Volcanic Explosivity Index (local data)	0					Physical measure: in event narratives only (local data needed).
Wildfire	acres burned (local data)	1 record, 2002		No damage reported in 1 record.		No event record names a jurisdiction in the plan.	Acres burned: in event narratives only (local data needed).
Winter Storm, Heavy Snow, Blizzard, Lake-Effect Snow, Winter Weather, Sleet	none in data (snowfall: local data)	133 records, 1996 to 2024 (133 zone-level)		No damage reported in 133 records.		Countywide (zone-level records).	Snow depth: in event narratives only (local data needed).

Storm Events records are more complete after 1996; before 1996 only Tornado (from 1950), Hail and Thunderstorm Wind (from 1955) exist. Zone-level records whose zone 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.

Supports FEMA checklist item B1-d: previous occurrences

Federal declarations for this county: 7 declarations covering 4 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

Declared	Incident began	FEMA number	Type	Title	Mapped hazard	County Public Assistancefederal share obligated, nominal dollars	Notes
2020-04-09	2020-01-20	DR-4534-ID	Major disaster	COVID-19 Pandemic	Non-natural, not counted	$34,250.42
2020-03-13	2020-01-20	EM-3467-ID	Emergency	COVID-19	Non-natural, not counted	no Public Assistance recorded	same incident as DR-4534
2012-09-18	2012-09-18	FM-5019-ID	Fire management	Karney Fire	Wildfire	no Public Assistance recorded
2005-09-13	2005-08-29	EM-3244-ID	Emergency	Hurricane Katrina	Hurricane: evacuation support, not a local hazard event; not counted	no Public Assistance recorded
2000-09-01	2000-07-27	DR-1341-ID	Major disaster	Wildfires	Wildfire	PA not declared for this county
1997-01-04	1996-11-16	DR-1154-ID	Major disaster	Severe Storms, Flooding, Mud and Landslides	Inland Flooding; Landslide	no Public Assistance recorded
1964-12-31	1964-12-31	DR-186-ID	Major disaster	Heavy Rains & Flooding	Inland Flooding	no 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

Declared	Incident began	FEMA number	Type	Title	Mapped hazard
1963-02-14	1963-02-14	DR-143-ID	Major disaster	Floods	Inland Flooding
1962-02-14	1962-02-14	DR-120-ID	Major disaster	Floods	Inland Flooding
1961-06-26	1961-06-26	DR-116-ID	Major disaster	Floods	Inland Flooding
1960-07-22	1960-07-22	DR-105-ID	Major disaster	Fires	Wildfire
1957-05-27	1957-05-27	DR-76-ID	Major disaster	Flood	Inland Flooding
1956-04-21	1956-04-21	DR-55-ID	Major disaster	Floods	Inland 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.

2 Fire Management declarations (1977-08-20 to 1979-08-08) FEMA filed as Statewide with no county; each names one local fire. Listed on the state page.

Public Assistance not placed in any Idaho county: 1 row, $107,969.35; listed on the Idaho state page.

Source: 3

Previous occurrences by hazard, with explicit no-event rows

Sources: 2, 6, 7

Hazard	Storm Events records, all years on file(years in the Period column)	In the 12 months before plan approvalrecords	Last 5 yearsrecords	Declared incidents, all yearsseparate disasters	Period	Statement
Avalanche	1	0	0	0	1996 to 2026-06-30
Cold Wave	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Drought	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Earthquake	0	0	0	0		Storm Events does not record earthquakes; the USGS earthquake catalog is the source.
Hail	21	0	2	0	1955 to 2026-06-30
Heat Wave	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Hurricane	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Ice Storm	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Inland Flooding	27	3	5	2	1996 to 2026-06-30
Landslide	5	0	2	1	1996 to 2026-06-30
Lightning	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Strong Wind	38	2	9	0	1955 to 2026-06-30	Includes 9 High Wind and 2 Strong Wind records.
Tornado	0	0	0	0	1950 to 2026-06-30	No recorded events, 1950 to 2026-06-30, NOAA NCEI Storm Events
Volcanic Activity	0	0	0	0	1996 to 2026-06-30	No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events
Wildfire	1	0	0	2	1996 to 2026-06-30
Winter Weather	133	0	19	0	1996 to 2026-06-30

Notable Storm Events records

Sources: 1, 6, 7

Date	Event type	Magnitude or extent	Damagenominal dollars	Deaths, injuriesdirect only	Location	Flags	Why listed
2025-12-17	High Wind	61 kt (70 mph) estimated gust	$0 property; $0 crops, reported for the zone (2025 dollars)	0, 0	NWS zone IDZ013 (BOISE MOUNTAINS), zone-level	in the 12 months before plan approval; within last 5 years	B1-c worst recorded: High Wind and Strong Wind
2014-08-06	Flood		$0 property; $8,000,000 crops (2014 dollars) (as recorded; larger than this county's annual agriculture value in the National Risk Index (the county or state extension service keeps crop loss records))	0, 0	IDAHO CITY		B1-c worst recorded: Flash Flood, Flood, Lakeshore Flood
2013-05-21	Strong Wind	49 kt (56 mph) estimated gust	$10,000 property; $0 crops, reported for the zone (2013 dollars)	0, 0	NWS zone IDZ013 (BOISE MOUNTAINS), zone-level		B1-c most damaging: High Wind and Strong Wind
2010-08-21	Thunderstorm Wind	61 kt (70 mph) estimated gust	$0 property; $0 crops (2010 dollars)	1, 0	IDAHO CITY to GRIMES		deaths or injuries recorded
2010-03-30	Avalanche		$0 property; $0 crops, reported for the zone (2010 dollars)	2, 0	NWS zone IDZ013 (BOISE MOUNTAINS), zone-level		deaths or injuries recorded
2008-07-22	Flash Flood		$100,000 property; $0 crops (2008 dollars)	0, 0	LOWMAN		large reported damage
2008-07-22	Thunderstorm Wind	78 kt (90 mph) measured gust	property not reported; $0 crops (2008 dollars)	0, 0	PLACERVILLE		B1-c worst recorded: Thunderstorm Wind
1993-08-10	Thunderstorm Wind	speed not recorded	damage not recorded (pre-1996 record)	0, 1	location not recorded		deaths or injuries recorded
1993-08-07	Thunderstorm Wind	speed not recorded	damage not recorded (pre-1996 record)	0, 4	location not recorded		deaths or injuries recorded
1993-05-03	Thunderstorm Wind	speed not recorded	$50,000 property; crops not recorded (1993 dollars)	0, 0	location not recorded		B1-c most damaging: Thunderstorm Wind
1987-06-15	Thunderstorm Wind	speed not recorded	damage not recorded (pre-1996 record)	0, 1	location not recorded		deaths or injuries recorded
1961-07-05	Hail	2 in	damage not recorded (pre-1996 record)	0, 0	location not recorded		B1-c worst recorded: Hail

The full list is in the Excel file, sheet "B1-d Storm Events history" (226 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).

Tribal and special-area declarations in this state are listed on the state page.

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

Probability: FEMA annualized frequency and descriptor per hazard

Sources: 5, 6

Hazard	FEMA annualized frequency (modeled)unit per row	Unit	In plain terms	Descriptor	Descriptor basis	NRI events or days in its record period (hail, wind and tornado are area-weighted, so can be fractional)	NRI period	Location	Note
Avalanche	0.1	events per year	about 1 in 10 years	Likely	FEMA annualized frequency (modeled)	3	1994 to 2023 (30 years)	see B1-f
Cold Wave	0.0534	event-days per year	about 0.0534 days per year		event-days in 0 of 30 years, 1996 to 2025 (0%)	1.02	2005-11-12 to 2024-11-12 (19 years)	countywide	No Storm Events cold wave record, 1996 to 2025.
Drought	7.8	event-days per year	about 7.8 days per year		event-days in 0 of 30 years, 1996 to 2025 (0%)	357	2000 to 2025 (25.25 years; D3 and D4 only)	countywide	No Storm Events drought record, 1996 to 2025
Earthquake	0.0103	annual probability at a location	chance a given location in the county has at least minor-damage shaking in a year: 1.03%			not shown	modeled	see B1-f	No descriptor (Storm Events does not record earthquakes).
Hail	0.197	events per year	about 1 in 5 years	Likely	FEMA annualized frequency (modeled)	7.5 (modeled)	1986 to 2023 (38 years)	countywide
Heat Wave	1.47	event-days per year	about 1.47 days per year		event-days in 0 of 30 years, 1996 to 2025 (0%)	21	2005-11-12 to 2024-11-12 (19 years)	countywide	No Storm Events heat wave record, 1996 to 2025
Hurricane		events per year					1851 to 2024 (Atlantic)	see B1-f	Not Applicable in NRI for this county; no descriptor.
Ice Storm	0.0425	event-days per year	about 0.0425 days per year		event-days in 0 of 30 years, 1996 to 2025 (0%)	3	1946-12-31 to 2014-02-12 (67 years)	countywide	No Storm Events ice storm record, 1996 to 2025
Inland Flooding	0.821	event-days per year	about 0.821 days per year	Likely (from Storm Events: 15 of 30 years)	event-days in 15 of 30 years, 1996 to 2025 (50%)	23	1996 to 2023 (28 years)	see B1-f
Landslide	2.09	events per year (modeled)	about 2.09 per year	Highly likely	FEMA annualized frequency (modeled)	not shown	modeled	see B1-f
Lightning	23.2	days per year with a strike	about 23.2 days per year	Highly likely	FEMA annualized frequency (modeled)	not shown	1995 to 2023 (29 years; CONUS)	countywide
Strong Wind	0.29	events per year	about 1 in 3 years	Likely	FEMA annualized frequency (modeled)	12	1986 to 2023 (38 years)	countywide
Tornado	0.0807	events per year	about 1 in 12 years	Possible	FEMA annualized frequency (modeled)	not shown	1950 to 2023 (EF2+); 1986 to 2023 (EF0-1)	see B1-f
Volcanic Activity	0.0002	annual probability	about 1 in 5,000 years	Unlikely	FEMA annualized frequency (modeled)	not shown	modeled	see B1-f
Wildfire	0.0174	annual probability at a location	chance a given location in the county burns in a year: 1.74%	Possible (from Storm Events: 1 of 30 years)	Storm Events records in 1 of 30 years, 1996 to 2025 (3.33%)	not shown	modeled	see B1-f	Descriptor from Storm Events, not NRI.
Winter Weather	17.7	event-days per year	about 17.7 days per year	Highly likely (from Storm Events: 27 of 30 years)	event-days in 27 of 30 years, 1996 to 2025 (90%)	336	2005-11-12 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.

Descriptor scale used in this packet (defined per unit)

Sources: 5, 6

Unit	Descriptor	Definition
events per year	Highly likely	1 or more per year
events per year	Likely	about once in 1 to 10 years
events per year	Possible	about once in 10 to 100 years
events per year	Unlikely	less than once in 100 years
annual probability	Likely	10% to under 100% chance in a given year
annual probability	Possible	1% to under 10% chance in a given year
annual probability	Unlikely	under 1% chance in a given year
event-days (share of years)	Highly likely	event-days recorded in 90% or more of years
event-days (share of years)	Likely	event-days recorded in 10% to under 90% of years
event-days (share of years)	Possible	event-days recorded in some years but under 10% of years
lightning strike-days	Highly likely	cloud-to-ground strikes on 1 or more days per year

Intensity bands: historical frequency (Storm Events)

Source: 6

Hazard	Band	Years	Eventscounty-coded records	Years in period	Events per yearevents / years
Hail	1.00-1.99 in	1996 to 2025	11	30	0.367
Hail	2.00 in+	1996 to 2025	0	30	0
Thunderstorm Wind (counted as NRI Strong Wind)	50-64 kt	1996 to 2025	17	30	0.567
Thunderstorm Wind (counted as NRI Strong Wind)	65 kt+	1996 to 2025	2	30	0.0667
Thunderstorm Wind (counted as NRI Strong Wind)	unmeasured or below 50 kt	1996 to 2025	1	30	0.0333
Tornado	EF0-1	1996 to 2025	0	30	0
Tornado	EF2-3	1996 to 2025	0	30	0
Tornado	EF4-5	1996 to 2025	0	30	0
Tornado	unrated (EFU)	1996 to 2025	0	30	0

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

Hazard	Tractsrated of all	NRI risk score, 0 to 100			Tracts by rating
Hazard	Tractsrated of all	Min	Median	Max	Tracts by rating
Avalanche	3 of 3	83.5	83.9	85.2	Relatively Moderate 3
Cold Wave	3 of 3	19.8	20.1	21.6	Relatively Low 3
Drought	2 of 3	67.0	67.4	67.8	Very Low 2, No Rating 1
Earthquake	3 of 3	28.1	60.6	74.7	Relatively Low 2, Very Low 1
Hail	3 of 3	35.6	38.1	44.9	Relatively Low 2, Very Low 1
Heat Wave	3 of 3	14.9	16.4	25.2	Relatively Low 1, Very Low 2
Hurricane	0 of 3				Not Applicable 3
Ice Storm	3 of 3	5.6	42.5	49.1	Relatively Low 2, Very Low 1
Inland Flooding	3 of 3	74.5	96.7	97.2	Very High 2, Relatively Moderate 1
Landslide	3 of 3	99.6	99.6	99.7	Relatively High 3
Lightning	3 of 3	45.0	46.3	59.0	Relatively Moderate 1, Relatively Low 2
Strong Wind	3 of 3	83.2	87.2	92.1	Relatively High 3
Tornado	3 of 3	9.4	10.0	16.0	Very Low 3
Volcanic Activity	3 of 3	47.6	66.1	69.0	Very Low 3
Wildfire	3 of 3	99.5	99.8	99.8	Very High 3
Winter Weather	3 of 3	93.3	94.1	96.7	Very High 1, Relatively High 2

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).

This county has 3 census tracts; the minimum, median and maximum come from those 3.

Each jurisdiction (starting figures from federal data)

Sources: 1, 3, 4, 6

Jurisdiction	Type	Plan status	Repetitive lossFMA RL and SRL (44 CFR 77.2); repeat-flood, any definition	Public Assistance to this jurisdictionFEMA records matched by applicant name; federal share obligated, nominal dollars	Event records naming this placeall years; since its plan
Boise County	County	Approved, expires 2031-05-26	FMA RL 0, SRL 0; any 0	no Public Assistance recorded	0 total; 0 since its plan
Crouch city	City	Plan 109978 approved 2026-05-27, pending adoption here; not yet eligible	FMA RL 0, SRL 0; any 0	no Public Assistance recorded	2 total; no approved plan
Horseshoe Bend city	City	Approved, expires 2031-05-26	FMA RL 0, SRL 0; any 0	no Public Assistance recorded	14 total; 0 since its plan
Idaho City city	City	Approved, expires 2031-05-26	FMA RL 0, SRL 0; any 0	no Public Assistance recorded	10 total; 0 since its plan
Placerville city	City	Plan 109978 approved 2026-05-27, pending adoption here; not yet eligible	FMA RL 0, SRL 0; any 0	no Public Assistance recorded	4 total; no approved plan

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

Hazard	Building exposuremodeled dollars	Agriculture exposuremodeled dollars	Population exposedpeople	EAL buildingsmodeled dollars per year	EAL agriculturemodeled dollars per year	Cost of expected deaths and injuriesFEMA's dollar value per year, not property damage	EAL as % of exposurebuildings; agriculture where noted	Note
Avalanche	$1,196,844	n/a	10	$4	n/a	$1,370,000	0.000301%
Cold Wave	$2,180,281,032	$3,329,382	7,582	$50	$103	$12,775	under 0.0001%
Drought	n/a	$210,931	n/a	n/a	$1	n/a	0.000608% (agriculture)	NRI has no building exposure for this hazard; agriculture shown
Earthquake	$3,560,938,791	n/a	7,610	$142,358	n/a	$15,926	0.004%
Hail	$2,180,281,032	$3,329,382	7,582	$9,152	$200	$1,246	0.00042%
Heat Wave	$2,180,281,032	$3,329,382	7,582	$12	$141	$36,107	under 0.0001%
Hurricane								Not Applicable in NRI for this county
Ice Storm	$2,180,281,032	n/a	7,582	$413	n/a	$7,338	under 0.0001%
Inland Flooding	$2,175,577,645	$117,500	335	$5,506,880	$151	$2,461	n/a (see note)	NRI 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	$400,278,885	n/a	1,473	$27,256	n/a	$328,733	0.00681%
Lightning	$2,180,281,032	n/a	7,582	$1,625	n/a	$30,061	under 0.0001%
Strong Wind	$2,180,281,032	$3,329,382	7,582	$4,009	$9	$220,618	0.000184%
Tornado	$2,180,281,032	$3,329,382	7,582	$7,926	$16	$5,190	0.000364%
Volcanic Activity	$2,180,281,032	n/a	7,582	under $1	n/a	$3	under 0.0001%
Wildfire	$1,455,254,351	$2,474,252	6,347	$7,908,596	$88	$331,961	0.543%
Winter Weather	$2,180,281,032	$3,329,382	7,582	$180	$44	$70,192	under 0.0001%

Totals since 2026-05-27 (Storm Events through 2026-06-30): 0 county-coded records, 0 with a damage value recorded (including $0), $0; 0 zone-level records, 0 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

Measure	Value
Population	7,582
Building value (total, not at risk)	$2,180,281,032
Agriculture value (total, not at risk)	$3,329,382
NRI risk rating (all hazards)	Relatively Low
Expected annual loss, buildings and agriculture, all hazards	$13,609,214
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)	$2,432,611
Social vulnerability rating	Relatively Low
Community resilience rating	Very Low
NRI version	December 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

Definition	Properties	Severe repetitive loss	Properties
Repetitive loss, FMA definition (44 CFR 77.2)	0	Severe repetitive loss, FMA definition (44 CFR 77.2)	0
Repetitive loss, NFIP insurance definition	0	Severe repetitive loss, NFIP insurance definition	0

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

Repeat-flood properties: county total and NFIP communities

Sources: 1, 4

Scope	RL, FMAproperties	SRL, FMAproperties	RL, NFIPproperties	SRL, NFIPproperties	Any categoryproperties	Mitigatedproperties	Currently insuredproperties
County total	0	0	0	0	0	0	0

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

Sources: 1, 4

Jurisdiction	NFIP community ID	RL, FMAproperties	SRL, FMAproperties	RL, NFIPproperties	SRL, NFIPproperties	Any categoryproperties	Mitigatedproperties	Currently insuredproperties
Boise County	160205	0	0	0	0	0	0	0
Crouch city	160247	0	0	0	0	0	0	0
Horseshoe Bend city	160172	0	0	0	0	0	0	0
Idaho City city	160222	0	0	0	0	0	0	0
Placerville city	160249	0	0	0	0	0	0	0

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: 0 in every occupancy group.

Sources: 1, 4

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 0 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):

FEMA, OpenFEMA HazardMitigationPlanStatuses v1, version 2026-09-29T134039Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/HazardMitigationPlanStatuses (API)
FEMA, OpenFEMA DisasterDeclarationsSummaries v2, version 2026-09-29T162832Z, pulled 2026-09-30, https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries (API)
FEMA, OpenFEMA PublicAssistanceFundedProjectsSummaries v1, version 2026-09-29T150754Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/PublicAssistanceFundedProjectsSummaries (API)
FEMA, OpenFEMA NfipMultipleLossProperties v1, version 2026-08-04T164045Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/NfipMultipleLossProperties (API)
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)
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/
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
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, organized by the items of FEMA's Local Mitigation Plan Review Tool, Element B. Each section heading names the item its tables support; the plan and FEMA's review decide whether the 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). Boise County, ID: risk-assessment baseline packet, release 2026-10 (data as of 2026-09-30; County FIPS 16015). Automated baseline. https://hazardplain.org/id/16015/ 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: [email protected]

Hazard Plain release 2026-10. As of 2026-09-30; Storm Events data through 2026-06-30. Automated baseline.