Orange County, California Natural Disaster Risk
FEMA National Risk Index assessment · CA
Very HighComposite Risk Score
National percentile: 100th
Orange County faces very high composite natural disaster risk (NRI Risk Index score 99.8, 100th national percentile), driven primarily by earthquake and riverine flood exposure. Expected annual loss across all 18 hazard types is $1.93B.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Orange County is very high, with a National Risk Index score of 99.8 out of 100 — placing it in the 100th national percentile and among the most at-risk counties in the United States. 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 earthquake (ground shaking from sudden movement along geologic faults) at Very High risk — $1.02B in expected annual loss and about 0.10 events per year; riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Very High risk — $820M in expected annual loss and about 2.89 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at High risk — $58M in expected annual loss and about 0.01 events per year. Across all hazards, FEMA estimates $1.93B in expected annual loss for a population of 3.18M.
Beyond physical exposure, Orange County has a low social vulnerability rating (how susceptible the population is to harm) and a very low 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: Orange County has received 42 federal disaster declarations since 1969, including 19 for fire events and 11 for flood events. The most recent was Chemical Release (chemical), declared in May 2026.
Among 58 California counties, Orange County ranks #4 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Earthquake | Very High | 0.10 / yr | $1.02B |
| Riverine Flood | Very High | 2.89 / yr | $820M |
| Wildfire | High | 0.01 / yr | $58M |
| Landslide | High | 17.84 / yr | $4M |
| Heat Wave | High | 7.41 / yr | $11M |
| Coastal Flood | High | 2.13 / yr | $8M |
| Tornado | Medium | 0.13 / yr | $5M |
| Hail | Medium | 0.10 / yr | $937K |
| Lightning | Medium | 7.43 / yr | $489K |
| Tsunami | Low | 0.39 / yr | $3M |
| Strong Wind | Medium | 0.17 / yr | $653K |
| Drought | Low | 62.64 / yr | $37K |
| Avalanche | Very Low | 0.01 / yr | $16 |
| Winter Weather | Very Low | 0.20 / yr | $133 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Hurricane | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Orange County has received 42 federal disaster declarations since 1969, most recently Chemical Release in May 2026. Most frequent causes: Fire (19), Flood (11), Severe Storm (5).
| Declared | Type | Disaster |
|---|---|---|
| May 2026 | Chemical | Chemical Release |
| March 2023 | Flood | Severe Winter Storms, Flooding, Landslides, and Mudslides |
| January 2023 | Flood | Severe Winter Storms, Flooding, and Mudslides |
| May 2022 | Fire | Coastal Fire |
| December 2020 | Fire | Bond Fire |
| October 2020 | Fire | Blue Ridge Fire |
| October 2020 | Fire | Silverado Fire |
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| October 2017 | Fire | Wildfires |
Showing the 10 most recent of 42 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Orange County?
Orange County has a composite FEMA National Risk Index score of 99.8 out of 100, placing it in the Very High category and the 100th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Orange County?
The three highest-rated hazards are Earthquake (Very High, $1.02B EAL), Riverine Flood (Very High, $820M EAL), Wildfire (High, $58M EAL). These account for most of the county's expected annual losses.
How does Orange County compare to other California counties?
Orange County ranks #4 of 58 California counties for overall natural disaster risk, with a very high rating.
How many federally declared disasters has Orange County had?
FEMA records 42 federal disaster declarations for Orange County since 1969, most often 19 for fire events and 11 for flood events. The most recent was Chemical Release, declared in May 2026.
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. Orange County's $1.93B EAL is a statistical average, not a guarantee for any specific year or address.