Arapahoe County, Colorado Natural Disaster Risk
FEMA National Risk Index assessment · CO
MediumComposite Risk Score
National percentile: 94th
Arapahoe County faces medium composite natural disaster risk (NRI Risk Index score 93.8, 94th national percentile), driven primarily by hail and lightning exposure. Expected annual loss across all 18 hazard types is $172M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
FEMA's National Risk Index rates Arapahoe County at medium composite risk, with a National Risk Index score of 93.8 out of 100 — placing it in the 94th national percentile and near the national midpoint for natural-disaster risk. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
The county's risk is driven primarily by hail (ice stones from severe thunderstorms that damage property and crops) at Very High risk — $64M in expected annual loss and about 8.62 events per year; lightning (electrical discharges from storms that ignite fires and cause casualties) at Very High risk — $4M in expected annual loss and about 51.51 events per year; and tornado (violently rotating columns of air capable of catastrophic local damage) at High risk — $22M in expected annual loss and about 1.06 events per year. Across all hazards, FEMA estimates $172M in expected annual loss for a population of 654K.
Beyond physical exposure, Arapahoe County has a very low social vulnerability rating (how susceptible the population is to harm) and a medium community resilience rating (its capacity to prepare for and recover from disasters). Both measures sit toward the lower end, indicating relatively modest population sensitivity.
History supports the rating: Arapahoe County has received 12 federal disaster declarations since 1965, including 5 for flood events and 2 for biological events. The most recent was Severe Storms, Flooding, and Tornadoes (flood), declared in August 2023.
Among 64 Colorado counties, Arapahoe County ranks #4 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Hail | Very High | 8.62 / yr | $64M |
| Lightning | Very High | 51.51 / yr | $4M |
| Tornado | High | 1.06 / yr | $22M |
| Strong Wind | High | 1.44 / yr | $4M |
| Riverine Flood | Medium | 1.32 / yr | $62M |
| Cold Wave | High | 1.61 / yr | $9M |
| Winter Weather | High | 12.70 / yr | $519K |
| Earthquake | Low | 0.00 / yr | $4M |
| Wildfire | Low | 0.00 / yr | $802K |
| Volcanic Activity | Very Low | 0.00 / yr | $155 |
| Heat Wave | Low | 0.73 / yr | $1M |
| Landslide | Very Low | 0.15 / yr | $2K |
| Drought | Low | 28.81 / yr | $118K |
| Ice Storm | Very Low | 0.03 / yr | $7K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
Disaster History
Arapahoe County has received 12 federal disaster declarations since 1965, most recently Severe Storms, Flooding, and Tornadoes in August 2023. Most frequent causes: Flood (5), Biological (2), Snowstorm (2).
| Declared | Type | Disaster |
|---|---|---|
| August 2023 | Flood | Severe Storms, Flooding, and Tornadoes |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| September 2013 | Flood | Severe Storms, Flooding, Landslides, and Mudslides |
| September 2013 | Flood | Severe Storms, Flooding, Landslides, and Mudslides |
| January 2007 | Snowstorm | Snow |
| September 2005 | Coastal Storm | Hurricane Katrina Evacuation |
| April 2003 | Snowstorm | Snow |
| June 2002 | Fire | Wildfires |
| May 1973 | Flood | Heavy Rains, Snowmelt and Flooding |
Showing the 10 most recent of 12 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Arapahoe County?
Arapahoe County has a composite FEMA National Risk Index score of 93.8 out of 100, placing it in the Medium category and the 94th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Arapahoe County?
The three highest-rated hazards are Hail (Very High, $64M EAL), Lightning (Very High, $4M EAL), Tornado (High, $22M EAL). These account for most of the county's expected annual losses.
How does Arapahoe County compare to other Colorado counties?
Arapahoe County ranks #4 of 64 Colorado counties for overall natural disaster risk, with a medium rating.
How many federally declared disasters has Arapahoe County had?
FEMA records 12 federal disaster declarations for Arapahoe County since 1965, most often 5 for flood events and 2 for biological events. The most recent was Severe Storms, Flooding, and Tornadoes, declared in August 2023.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Arapahoe County's $172M EAL is a statistical average, not a guarantee for any specific year or address.