Arizona heat wave risk
Maricopa County has the highest heat wave risk in Arizona, scoring 100 out of 100 — rated "Very High" by FEMA's National Risk Index. Recorded heat wave events across Arizona have increased 24% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Maricopa County | 100 | Very High | 99 |
| 2 | Pima County | 99.8 | Very High | 98 |
| 3 | Cochise County | 99.1 | Relatively High | 45 |
| 4 | Santa Cruz County | 99 | Relatively High | 51 |
| 5 | Pinal County | 98.9 | Relatively High | 42 |
| 6 | Mohave County | 98.6 | Relatively High | 0 |
| 7 | Yuma County | 96.7 | Relatively High | 38 |
| 8 | Graham County | 95 | Relatively Moderate | 44 |
| 9 | La Paz County | 90.2 | Relatively Moderate | 46 |
| 10 | Gila County | 86.7 | Relatively Moderate | 1 |
| 11 | Yavapai County | 85 | Relatively Moderate | 1 |
| 12 | Coconino County | 63.9 | Relatively Low | 0 |
| 13 | Greenlee County | 60.4 | Relatively Low | 1 |
| 14 | Navajo County | 56.7 | Relatively Low | 0 |
| 15 | Apache County | 46.7 | Relatively Low | 0 |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties. See the methodology page for definitions. Download the full CSV for all counties.
Heat Wave risk nationally:
Other hazard risks in Arizona:
Frequently asked questions
What is the highest heat wave risk county in Arizona?
Maricopa County, AZ has the highest heat wave risk in Arizona, with a FEMA National Risk Index score of 100 out of 100 (rated "Very High").
How many counties in Arizona are rated Very High for heat wave risk?
2 of 15 scored Arizona counties are rated "Very High" for heat wave risk by FEMA's National Risk Index.
What causes heat wave risk in Arizona?
Heat is consistently the leading cause of weather-related mortality in the US, yet it remains underrepresented in federal disaster declarations relative to its actual impact. High scores reflect a combination of extreme temperature exposure, population vulnerability (elderly, outdoor workers), and limited access to cooling infrastructure.