Iowa tornado risk
99 counties scored 0 rated Very High
Johnson County has the highest tornado risk in Iowa, scoring 98.2 out of 100 — rated "Relatively High" by FEMA's National Risk Index. Recorded tornado events across Iowa have increased 69% over the past five years compared to the prior five-year period.
| # | County | NRI score | Rating |
NOAA events 2016–2026 |
|---|---|---|---|---|
| 1 | Johnson County | 98.2 | Relatively High | 13 |
| 2 | Polk County | 98.1 | Relatively High | 16 |
| 3 | Woodbury County | 96.5 | Relatively High | 5 |
| 4 | Linn County | 95.5 | Relatively High | 19 |
| 5 | Pottawattamie County | 95.2 | Relatively High | 17 |
| 6 | Webster County | 92.1 | Relatively High | 18 |
| 7 | Black Hawk County | 91.4 | Relatively High | 4 |
| 8 | Story County | 91.3 | Relatively High | 10 |
| 9 | Cerro Gordo County | 89.3 | Relatively Moderate | 9 |
| 10 | Carroll County | 85.5 | Relatively Moderate | 4 |
| 11 | Dallas County | 84.7 | Relatively Moderate | 9 |
| 12 | Dubuque County | 84 | Relatively Moderate | 9 |
| 13 | Scott County | 82.9 | Relatively Moderate | 21 |
| 14 | Marshall County | 82.7 | Relatively Moderate | 6 |
| 15 | Crawford County | 82.4 | Relatively Moderate | 5 |
| 16 | Wapello County | 81.8 | Relatively Moderate | 2 |
| 17 | Sioux County | 79.4 | Relatively Moderate | 9 |
| 18 | Clinton County | 79 | Relatively Moderate | 18 |
| 19 | Plymouth County | 77.4 | Relatively Moderate | 5 |
| 20 | Cass County | 75.8 | Relatively Moderate | 11 |
| 21 | Buena Vista County | 74 | Relatively Moderate | 9 |
| 22 | Calhoun County | 73.6 | Relatively Moderate | 9 |
| 23 | Appanoose County | 73.1 | Relatively Moderate | 5 |
| 24 | Hardin County | 72.2 | Relatively Moderate | 12 |
| 25 | Fayette County | 71.5 | Relatively Moderate | 3 |
| 26 | Jasper County | 70.3 | Relatively Moderate | 15 |
| 27 | Lee County | 70.3 | Relatively Moderate | 10 |
| 28 | Page County | 69.6 | Relatively Moderate | 7 |
| 29 | Des Moines County | 69.4 | Relatively Moderate | 6 |
| 30 | Davis County | 68.7 | Relatively Moderate | 2 |
| 31 | Floyd County | 68 | Relatively Moderate | 11 |
| 32 | Marion County | 67.7 | Relatively Moderate | 18 |
| 33 | Warren County | 65.9 | Relatively Moderate | 11 |
| 34 | Greene County | 65.5 | Relatively Moderate | 10 |
| 35 | Hamilton County | 64.8 | Relatively Low | 9 |
| 36 | Guthrie County | 64.1 | Relatively Low | 12 |
| 37 | Dickinson County | 64 | Relatively Low | 5 |
| 38 | Shelby County | 63.2 | Relatively Low | 7 |
| 39 | Adair County | 62.4 | Relatively Low | 9 |
| 40 | Montgomery County | 61.6 | Relatively Low | 8 |
| 41 | Kossuth County | 61.1 | Relatively Low | 4 |
| 42 | Cherokee County | 60.8 | Relatively Low | 4 |
| 43 | Winneshiek County | 60.8 | Relatively Low | 6 |
| 44 | Harrison County | 60.1 | Relatively Low | 12 |
| 45 | Sac County | 60 | Relatively Low | 8 |
| 46 | Iowa County | 59.9 | Relatively Low | 5 |
| 47 | Poweshiek County | 59.8 | Relatively Low | 9 |
| 48 | Audubon County | 59.7 | Relatively Low | 3 |
| 49 | Chickasaw County | 59.3 | Relatively Low | 3 |
| 50 | Ida County | 59.1 | Relatively Low | 4 |
| 51 | Delaware County | 58.5 | Relatively Low | 10 |
| 52 | Monona County | 58 | Relatively Low | 3 |
| 53 | Tama County | 57.4 | Relatively Low | 5 |
| 54 | Lucas County | 57.3 | Relatively Low | 4 |
| 55 | Boone County | 57.2 | Relatively Low | 11 |
| 56 | Union County | 57.1 | Relatively Low | 11 |
| 57 | Washington County | 57 | Relatively Low | 5 |
| 58 | Mills County | 55.9 | Relatively Low | 7 |
| 59 | Allamakee County | 55.7 | Relatively Low | 3 |
| 60 | Wayne County | 55.2 | Relatively Low | 5 |
| 61 | Muscatine County | 55 | Relatively Low | 6 |
| 62 | Madison County | 54.9 | Relatively Low | 11 |
| 63 | Jackson County | 54.8 | Relatively Low | 12 |
| 64 | Van Buren County | 54.7 | Relatively Low | 5 |
| 65 | Mahaska County | 54.6 | Relatively Low | 4 |
| 66 | Wright County | 54.4 | Relatively Low | 9 |
| 67 | Taylor County | 54.3 | Relatively Low | 7 |
| 68 | Jefferson County | 54.1 | Relatively Low | 1 |
| 69 | Clayton County | 54 | Relatively Low | 3 |
| 70 | Clay County | 53.8 | Relatively Low | 0 |
| 71 | Bremer County | 52.3 | Relatively Low | 3 |
| 72 | Jones County | 51 | Relatively Low | 19 |
| 73 | Hancock County | 50.5 | Relatively Low | 3 |
| 74 | Franklin County | 50.3 | Relatively Low | 7 |
| 75 | Pocahontas County | 49.7 | Relatively Low | 16 |
| 76 | O'Brien County | 48.7 | Relatively Low | 3 |
| 77 | Henry County | 48.5 | Relatively Low | 4 |
| 78 | Butler County | 48.3 | Relatively Low | 4 |
| 79 | Decatur County | 48.3 | Relatively Low | 2 |
| 80 | Mitchell County | 47.7 | Relatively Low | 3 |
| 81 | Lyon County | 45.9 | Relatively Low | 6 |
| 82 | Winnebago County | 45.8 | Relatively Low | 4 |
| 83 | Fremont County | 45.7 | Relatively Low | 7 |
| 84 | Cedar County | 45.6 | Relatively Low | 13 |
| 85 | Humboldt County | 45.5 | Relatively Low | 8 |
| 86 | Clarke County | 44.6 | Relatively Low | 4 |
| 87 | Benton County | 43.6 | Relatively Low | 20 |
| 88 | Emmet County | 43.2 | Relatively Low | 2 |
| 89 | Osceola County | 42.7 | Relatively Low | 5 |
| 90 | Keokuk County | 42.3 | Relatively Low | 4 |
| 91 | Howard County | 40.6 | Relatively Low | 12 |
| 92 | Monroe County | 39.9 | Relatively Low | 1 |
| 93 | Palo Alto County | 38.8 | Relatively Low | 1 |
| 94 | Adams County | 38 | Relatively Low | 10 |
| 95 | Buchanan County | 37.5 | Relatively Low | 11 |
| 96 | Worth County | 36 | Relatively Low | 6 |
| 97 | Grundy County | 34.8 | Relatively Low | 7 |
| 98 | Louisa County | 34.2 | Relatively Low | 3 |
| 99 | Ringgold County | 31.5 | Relatively Low | 6 |
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.
Tornado risk nationally:
Other hazard risks in Iowa:
Frequently asked questions
What is the highest tornado risk county in Iowa?
Johnson County, IA has the highest tornado risk in Iowa, with a FEMA National Risk Index score of 98.2 out of 100 (rated "Relatively High").
What causes tornado risk in Iowa?
Tornado risk concentrates in the central and southern plains ("Tornado Alley") and the Southeast ("Dixie Alley"), where atmospheric conditions favor supercell thunderstorm development. The highest scores often belong to counties with significant mobile home and manufactured housing stock, which carries disproportionate tornado mortality risk.