Iowa heat wave risk
Polk County has the highest heat wave risk in Iowa, scoring 96.7 out of 100 — rated "Relatively High" by FEMA's National Risk Index. Recorded heat wave events across Iowa have increased 25% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Polk County | 96.7 | Relatively High | 3 |
| 2 | Johnson County | 87.5 | Relatively Moderate | 0 |
| 3 | Scott County | 86.9 | Relatively Moderate | 0 |
| 4 | Page County | 85.7 | Relatively Moderate | 9 |
| 5 | Lee County | 84.9 | Relatively Moderate | 0 |
| 6 | Pottawattamie County | 83.7 | Relatively Moderate | 8 |
| 7 | Des Moines County | 83.4 | Relatively Moderate | 0 |
| 8 | Woodbury County | 83.2 | Relatively Moderate | 21 |
| 9 | Union County | 82.7 | Relatively Moderate | 2 |
| 10 | Taylor County | 81.5 | Relatively Moderate | 2 |
| 11 | Henry County | 81 | Relatively Moderate | 0 |
| 12 | Jefferson County | 79.5 | Relatively Moderate | 0 |
| 13 | Muscatine County | 76.5 | Relatively Low | 0 |
| 14 | Davis County | 75.7 | Relatively Low | 2 |
| 15 | Wapello County | 75.1 | Relatively Low | 2 |
| 16 | Dallas County | 74.7 | Relatively Low | 2 |
| 17 | Van Buren County | 74.2 | Relatively Low | 0 |
| 18 | Cass County | 71.8 | Relatively Low | 2 |
| 19 | Montgomery County | 69.8 | Relatively Low | 11 |
| 20 | Appanoose County | 69.5 | Relatively Low | 2 |
| 21 | Linn County | 69.2 | Relatively Low | 0 |
| 22 | Warren County | 65.5 | Relatively Low | 2 |
| 23 | Washington County | 64.7 | Relatively Low | 0 |
| 24 | Decatur County | 63.6 | Relatively Low | 2 |
| 25 | Ringgold County | 63.2 | Relatively Low | 2 |
| 26 | Marion County | 61.5 | Relatively Low | 2 |
| 27 | Dubuque County | 61 | Relatively Low | 0 |
| 28 | Adair County | 59.5 | Relatively Low | 2 |
| 29 | Lucas County | 54.9 | Relatively Low | 2 |
| 30 | Mahaska County | 54.9 | Relatively Low | 2 |
| 31 | Clarke County | 54.3 | Relatively Low | 2 |
| 32 | Clinton County | 54.2 | Relatively Low | 0 |
| 33 | Adams County | 53 | Relatively Low | 2 |
| 34 | Wayne County | 52.7 | Relatively Low | 2 |
| 35 | Louisa County | 52.2 | Relatively Low | 0 |
| 36 | Keokuk County | 52 | Relatively Low | 0 |
| 37 | Fremont County | 51.8 | Relatively Low | 10 |
| 38 | Madison County | 51.7 | Relatively Low | 2 |
| 39 | Jasper County | 50.1 | Relatively Low | 2 |
| 40 | Iowa County | 49.7 | Relatively Low | 0 |
| 41 | Poweshiek County | 48.7 | Relatively Low | 2 |
| 42 | Black Hawk County | 44.8 | Relatively Low | 1 |
| 43 | Allamakee County | 43.4 | Relatively Low | 5 |
| 44 | Clayton County | 42.6 | Relatively Low | 5 |
| 45 | Cedar County | 42.5 | Relatively Low | 0 |
| 46 | Monroe County | 42.4 | Relatively Low | 2 |
| 47 | Plymouth County | 41.7 | Relatively Low | 20 |
| 48 | Sioux County | 40.7 | Relatively Low | 20 |
| 49 | Fayette County | 40.3 | Relatively Low | 5 |
| 50 | Mills County | 40 | Relatively Low | 6 |
| 51 | Audubon County | 36.6 | Very Low | 2 |
| 52 | Shelby County | 36.2 | Very Low | 9 |
| 53 | Jackson County | 35.6 | Very Low | 0 |
| 54 | Winneshiek County | 34.6 | Very Low | 5 |
| 55 | Delaware County | 34 | Very Low | 0 |
| 56 | Monona County | 31.7 | Very Low | 4 |
| 57 | Dickinson County | 31.5 | Very Low | 17 |
| 58 | Crawford County | 30.7 | Very Low | 2 |
| 59 | Guthrie County | 30 | Very Low | 2 |
| 60 | Lyon County | 29.9 | Very Low | 19 |
| 61 | Cherokee County | 27.8 | Very Low | 18 |
| 62 | Osceola County | 26.5 | Very Low | 18 |
| 63 | Buena Vista County | 26.3 | Very Low | 18 |
| 64 | Emmet County | 24.8 | Very Low | 2 |
| 65 | Buchanan County | 24.7 | Very Low | 0 |
| 66 | Jones County | 24.4 | Very Low | 0 |
| 67 | Ida County | 24.2 | Very Low | 19 |
| 68 | Chickasaw County | 22.1 | Very Low | 4 |
| 69 | Tama County | 21.6 | Very Low | 2 |
| 70 | O'Brien County | 21 | Very Low | 18 |
| 71 | Floyd County | 20.9 | Very Low | 4 |
| 72 | Carroll County | 20.4 | Very Low | 2 |
| 73 | Cerro Gordo County | 19.9 | Very Low | 2 |
| 74 | Harrison County | 19.4 | Very Low | 5 |
| 75 | Bremer County | 18.4 | Very Low | 1 |
| 76 | Calhoun County | 17.7 | Very Low | 2 |
| 77 | Benton County | 17.5 | Very Low | 0 |
| 78 | Howard County | 16.7 | Very Low | 4 |
| 79 | Clay County | 16.6 | Very Low | 17 |
| 80 | Mitchell County | 16.2 | Very Low | 4 |
| 81 | Sac County | 16.2 | Very Low | 2 |
| 82 | Greene County | 15.7 | Very Low | 2 |
| 83 | Webster County | 13.6 | Very Low | 2 |
| 84 | Pocahontas County | 13.2 | Very Low | 2 |
| 85 | Story County | 13 | Very Low | 2 |
| 86 | Butler County | 12.8 | Very Low | 1 |
| 87 | Hardin County | 11.1 | Very Low | 2 |
| 88 | Winnebago County | 10.8 | Very Low | 2 |
| 89 | Hamilton County | 10.7 | Very Low | 2 |
| 90 | Wright County | 10.5 | Very Low | 2 |
| 91 | Kossuth County | 10.1 | Very Low | 2 |
| 92 | Marshall County | 10.1 | Very Low | 2 |
| 93 | Palo Alto County | 10 | Very Low | 2 |
| 94 | Worth County | 9.5 | Very Low | 2 |
| 95 | Grundy County | 9.4 | Very Low | 1 |
| 96 | Humboldt County | 9.4 | Very Low | 2 |
| 97 | Hancock County | 9 | Very Low | 2 |
| 98 | Franklin County | 8.3 | Very Low | 2 |
| 99 | Boone County | 7.6 | Very Low | 2 |
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 Iowa:
Frequently asked questions
What is the highest heat wave risk county in Iowa?
Polk County, IA has the highest heat wave risk in Iowa, with a FEMA National Risk Index score of 96.7 out of 100 (rated "Relatively High").
What causes heat wave risk in Iowa?
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.