Maricopa County, Arizona Natural Disaster Risk
FEMA National Risk Index assessment · AZ
Very HighComposite Risk Score
National percentile: 100th
Maricopa County faces very high composite natural disaster risk (NRI Risk Index score 99.9, 100th national percentile), driven primarily by heat wave and riverine flood exposure. Expected annual loss across all 18 hazard types is $2.20B.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Overall natural disaster risk in Maricopa County is very high, with a National Risk Index score of 99.9 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 heat wave (prolonged periods of extreme heat that threaten health and infrastructure) at Very High risk — $958M in expected annual loss and about 19.83 events per year; riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Very High risk — $1.12B in expected annual loss and about 8.46 events per year; and wildfire (uncontrolled fires that spread across wildland and into communities) at High risk — $42M in expected annual loss and about 0.00 events per year. Across all hazards, FEMA estimates $2.20B in expected annual loss for a population of 4.42M.
Beyond physical exposure, Maricopa 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: Maricopa County has received 26 federal disaster declarations since 1966, including 11 for fire events and 9 for flood events. The most recent was Boulder View Fire (fire), declared in June 2024.
Among 15 Arizona counties, Maricopa County ranks #1 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Heat Wave | Very High | 19.83 / yr | $958M |
| Riverine Flood | Very High | 8.46 / yr | $1.12B |
| Wildfire | High | 0.00 / yr | $42M |
| Hail | Very High | 0.28 / yr | $24M |
| Strong Wind | Very High | 1.40 / yr | $9M |
| Drought | High | 62.54 / yr | $5M |
| Earthquake | Medium | 0.01 / yr | $31M |
| Lightning | High | 32.26 / yr | $2M |
| Tornado | Medium | 0.57 / yr | $5M |
| Landslide | Low | 2.11 / yr | $28K |
| Winter Weather | Low | 0.57 / yr | $47K |
| Avalanche | Very Low | 0.01 / yr | $144 |
| Hurricane | Very Low | 0.01 / yr | $12K |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Cold Wave | Very Low | 0.00 / yr | $0 |
| Ice Storm | Very Low | 0.00 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Maricopa County has received 26 federal disaster declarations since 1966, most recently Boulder View Fire in June 2024. Most frequent causes: Fire (11), Flood (9), Severe Storm (3).
| Declared | Type | Disaster |
|---|---|---|
| June 2024 | Fire | Boulder View Fire |
| June 2024 | Fire | Rose Fire |
| June 2023 | Fire | Diamond Fire |
| June 2020 | Fire | Avondale Fire |
| June 2020 | Fire | Aquila Fire |
| June 2020 | Fire | Bush Fire |
| May 2020 | Fire | Ocotillo Fire |
| May 2020 | Fire | East Desert Fire |
| April 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
Showing the 10 most recent of 26 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Maricopa County?
Maricopa County has a composite FEMA National Risk Index score of 99.9 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 Maricopa County?
The three highest-rated hazards are Heat Wave (Very High, $958M EAL), Riverine Flood (Very High, $1.12B EAL), Wildfire (High, $42M EAL). These account for most of the county's expected annual losses.
How does Maricopa County compare to other Arizona counties?
Maricopa County ranks #1 of 15 Arizona counties for overall natural disaster risk, with a very high rating.
How many federally declared disasters has Maricopa County had?
FEMA records 26 federal disaster declarations for Maricopa County since 1966, most often 11 for fire events and 9 for flood events. The most recent was Boulder View Fire, declared in June 2024.
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. Maricopa County's $2.20B EAL is a statistical average, not a guarantee for any specific year or address.