South Dakota cold wave risk
Dewey County has the highest cold wave risk in South Dakota, scoring 99 out of 100 — rated "Very High" by FEMA's National Risk Index.
| # | County | NRI score | Rating |
|---|---|---|---|
| 1 | Dewey County | 99 | Very High |
| 2 | Brown County | 96.4 | Relatively High |
| 3 | Brule County | 96.4 | Relatively High |
| 4 | Minnehaha County | 96 | Relatively High |
| 5 | Corson County | 91.8 | Relatively High |
| 6 | Walworth County | 88.8 | Relatively Moderate |
| 7 | Ziebach County | 87.8 | Relatively Moderate |
| 8 | Charles Mix County | 87.2 | Relatively Moderate |
| 9 | Pennington County | 85.7 | Relatively Moderate |
| 10 | Tripp County | 83.3 | Relatively Moderate |
| 11 | Codington County | 82.3 | Relatively Moderate |
| 12 | Roberts County | 80 | Relatively Moderate |
| 13 | Lyman County | 79.6 | Relatively Moderate |
| 14 | Grant County | 78.4 | Relatively Moderate |
| 15 | Buffalo County | 77.4 | Relatively Moderate |
| 16 | Beadle County | 77.3 | Relatively Moderate |
| 17 | Aurora County | 77.1 | Relatively Moderate |
| 18 | Brookings County | 77 | Relatively Moderate |
| 19 | Todd County | 76.4 | Relatively Moderate |
| 20 | Day County | 76 | Relatively Moderate |
| 21 | Gregory County | 75.7 | Relatively Moderate |
| 22 | Yankton County | 73.3 | Relatively Moderate |
| 23 | McPherson County | 71.7 | Relatively Moderate |
| 24 | Oglala Lakota County | 71.3 | Relatively Moderate |
| 25 | Marshall County | 70.6 | Relatively Moderate |
| 26 | Potter County | 70.5 | Relatively Moderate |
| 27 | Jerauld County | 69.1 | Relatively Moderate |
| 28 | Davison County | 67.1 | Relatively Moderate |
| 29 | Hutchinson County | 67 | Relatively Moderate |
| 30 | Spink County | 66.6 | Relatively Moderate |
| 31 | Faulk County | 65.4 | Relatively Low |
| 32 | Lake County | 65 | Relatively Low |
| 33 | Douglas County | 62.6 | Relatively Low |
| 34 | Butte County | 61.1 | Relatively Low |
| 35 | Meade County | 59.5 | Relatively Low |
| 36 | Hand County | 59.4 | Relatively Low |
| 37 | Haakon County | 59 | Relatively Low |
| 38 | Lincoln County | 58.9 | Relatively Low |
| 39 | Lawrence County | 58.3 | Relatively Low |
| 40 | Clark County | 56.5 | Relatively Low |
| 41 | Edmunds County | 55.4 | Relatively Low |
| 42 | Kingsbury County | 53.8 | Relatively Low |
| 43 | Jackson County | 53.3 | Relatively Low |
| 44 | Sully County | 51.1 | Relatively Low |
| 45 | Hughes County | 51 | Relatively Low |
| 46 | Bon Homme County | 50.8 | Relatively Low |
| 47 | Turner County | 50.6 | Relatively Low |
| 48 | Hamlin County | 50.2 | Relatively Low |
| 49 | Perkins County | 50.2 | Relatively Low |
| 50 | Hyde County | 47.9 | Relatively Low |
| 51 | Moody County | 47.4 | Relatively Low |
| 52 | Hanson County | 47.3 | Relatively Low |
| 53 | Deuel County | 46.7 | Relatively Low |
| 54 | Campbell County | 45.5 | Relatively Low |
| 55 | Mellette County | 43.4 | Relatively Low |
| 56 | Bennett County | 42.6 | Relatively Low |
| 57 | Fall River County | 42.2 | Relatively Low |
| 58 | McCook County | 38.5 | Relatively Low |
| 59 | Union County | 34.8 | Relatively Low |
| 60 | Miner County | 34.3 | Relatively Low |
| 61 | Sanborn County | 26.9 | Relatively Low |
| 62 | Custer County | 23.3 | Very Low |
| 63 | Clay County | 22.9 | Very Low |
| 64 | Jones County | 22.1 | Very Low |
| 65 | Harding County | 21.5 | Very Low |
| 66 | Stanley County | 19.4 | Very Low |
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.
Cold Wave risk nationally:
Other hazard risks in South Dakota:
Frequently asked questions
What is the highest cold wave risk county in South Dakota?
Dewey County, SD has the highest cold wave risk in South Dakota, with a FEMA National Risk Index score of 99 out of 100 (rated "Very High").
How many counties in South Dakota are rated Very High for cold wave risk?
1 of 66 scored South Dakota counties are rated "Very High" for cold wave risk by FEMA's National Risk Index.
What causes cold wave risk in South Dakota?
Cold wave risk captures expected losses from extended periods of extreme cold, including wind chill. The northern Plains, Great Lakes, and interior New England see the most severe and frequent cold events. Cold extremes cause significant excess mortality, especially among unhoused populations, the elderly, and those with inadequate heating or insulation. Cold and wind chill events are reported at forecast-zone level in NOAA Storm Events and are not included in county-level counts.