California heat wave risk
Kern County has the highest heat wave risk in California, scoring 99.5 out of 100 — rated "Relatively High" by FEMA's National Risk Index. Recorded heat wave events across California have increased 102% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Kern County | 99.5 | Relatively High | 24 |
| 2 | Los Angeles County | 99.3 | Relatively High | 0 |
| 3 | Tulare County | 99.2 | Relatively High | 7 |
| 4 | San Diego County | 98.7 | Relatively High | 53 |
| 5 | Santa Clara County | 98.6 | Relatively High | 1 |
| 6 | Riverside County | 98.5 | Relatively High | 58 |
| 7 | Mariposa County | 98.4 | Relatively High | 6 |
| 8 | San Bernardino County | 98.4 | Relatively High | 30 |
| 9 | Contra Costa County | 98.3 | Relatively High | 1 |
| 10 | Fresno County | 97.9 | Relatively High | 24 |
| 11 | Kings County | 97.9 | Relatively High | 24 |
| 12 | Inyo County | 97.8 | Relatively High | 54 |
| 13 | Madera County | 97.8 | Relatively High | 17 |
| 14 | Merced County | 97.7 | Relatively High | 24 |
| 15 | Alameda County | 97.6 | Relatively High | 16 |
| 16 | San Joaquin County | 97.4 | Relatively High | 0 |
| 17 | Orange County | 97.2 | Relatively High | 43 |
| 18 | Stanislaus County | 96.3 | Relatively Moderate | 0 |
| 19 | Sacramento County | 96.1 | Relatively Moderate | 0 |
| 20 | Monterey County | 95.8 | Relatively Moderate | 2 |
| 21 | Imperial County | 94 | Relatively Moderate | 47 |
| 22 | San Francisco County | 93.9 | Relatively Moderate | 6 |
| 23 | San Mateo County | 91.6 | Relatively Moderate | 3 |
| 24 | Tuolumne County | 89 | Relatively Moderate | 0 |
| 25 | Sonoma County | 88.8 | Relatively Moderate | 2 |
| 26 | Santa Cruz County | 86.6 | Relatively Moderate | 2 |
| 27 | Ventura County | 85.8 | Relatively Moderate | 0 |
| 28 | Shasta County | 85.7 | Relatively Moderate | 0 |
| 29 | Calaveras County | 84.1 | Relatively Moderate | 0 |
| 30 | Butte County | 82 | Relatively Moderate | 0 |
| 31 | Sutter County | 80.1 | Relatively Moderate | 0 |
| 32 | San Luis Obispo County | 78.7 | Relatively Low | 0 |
| 33 | Yolo County | 78.6 | Relatively Low | 0 |
| 34 | Siskiyou County | 77.8 | Relatively Low | 14 |
| 35 | Amador County | 77.3 | Relatively Low | 0 |
| 36 | Solano County | 77 | Relatively Low | 0 |
| 37 | Santa Barbara County | 75.4 | Relatively Low | 0 |
| 38 | Glenn County | 74.8 | Relatively Low | 0 |
| 39 | Marin County | 74.6 | Relatively Low | 0 |
| 40 | Placer County | 68.8 | Relatively Low | 0 |
| 41 | El Dorado County | 68 | Relatively Low | 0 |
| 42 | Napa County | 66.8 | Relatively Low | 1 |
| 43 | Colusa County | 65.4 | Relatively Low | 0 |
| 44 | San Benito County | 59.9 | Relatively Low | 6 |
| 45 | Nevada County | 57.8 | Relatively Low | 0 |
| 46 | Tehama County | 57.2 | Relatively Low | 0 |
| 47 | Yuba County | 54.1 | Relatively Low | 0 |
| 48 | Lake County | 52.6 | Relatively Low | 0 |
| 49 | Mendocino County | 52.4 | Relatively Low | 0 |
| 50 | Humboldt County | 47.3 | Relatively Low | 0 |
| 51 | Trinity County | 39.8 | Relatively Low | 0 |
| 52 | Modoc County | 29.8 | Very Low | 4 |
| 53 | Plumas County | 27.1 | Very Low | 0 |
| 54 | Lassen County | 24.2 | Very Low | 0 |
| 55 | Mono County | 23.4 | Very Low | 0 |
| 56 | Del Norte County | 14.9 | Very Low | 0 |
| 57 | Sierra County | 7.5 | Very Low | 0 |
| 58 | Alpine County | 4.6 | Very 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 California:
Frequently asked questions
What is the highest heat wave risk county in California?
Kern County, CA has the highest heat wave risk in California, with a FEMA National Risk Index score of 99.5 out of 100 (rated "Relatively High").
What causes heat wave risk in California?
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.