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Weather & Climate in Williamson, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Williamson experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 21°F in January while summers reach 73°F in July. The area gets 275 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 37.3 inches. The area receives 24.1 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 1,025 feet.
Temperature
21°F Jan (-6°C)
73°F Jul (23°C)
| Annual Average | 48.3°F |
| 11% below US avg | |
| January Average | 21°F (-6°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 1,025 ft (312 m) |
| Area | 0.4 sq mi (1.0 km²) |
| Population Density | 600/sq mi |
| Coordinates | 41.0882°N, 93.2570°W |
| Timezone | America/Chicago |
| County | Lucas County County |
| Nearest Airport | Des Moines International (DSM) 37 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 29.7 / 100 |
| Social Vulnerability | 69.1 / 100 |
| Community Resilience | 81.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Very Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Low |
| Heat Wave | Relatively Low |
| Winter Weather | Very Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively High |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Tornado History
565 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 24 fatalities, 308 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Mar 5, 2022 | EF4 | 81 km | 70.6 mi | 6 |
| Apr 8, 1999 | EF4 | 89 km | 56.0 mi | 0 |
| May 27, 1995 | EF4 | 98 km | 57.0 mi | 0 |
| Sep 28, 1986 | EF4 | 79 km | 20.0 mi | 0 |
| Jun 7, 1984 | EF4 | 99 km | 134.0 mi | 3 |
| Jun 2, 1980 | EF4 | 76 km | 31.2 mi | 0 |
| Jun 18, 1974 | EF4 | 78 km | 15.3 mi | 2 |
| Apr 21, 1973 | EF4 | 88 km | 14.6 mi | 0 |
| Jan 24, 1967 | EF4 | 98 km | 25.7 mi | 0 |
| May 20, 1959 | EF4 | 44 km | 17.2 mi | 0 |
| May 10, 1953 | EF4 | 25 km | 6.4 mi | 0 |
| Mar 31, 2023 | EF3 | 78 km | 26.1 mi | 0 |
| Mar 5, 2022 | EF3 | 20 km | 11.3 mi | 1 |
| Aug 20, 2019 | EF3 | 29 km | 5.4 mi | 0 |
| Jul 19, 2018 | EF3 | 49 km | 9.2 mi | 0 |
| Jun 22, 2015 | EF3 | 15 km | 11.1 mi | 0 |
| Apr 8, 1999 | EF3 | 22 km | 39.0 mi | 0 |
| Apr 8, 1999 | EF3 | 80 km | 16.0 mi | 0 |
| May 27, 1995 | EF3 | 85 km | 30.4 mi | 0 |
| Mar 22, 1991 | EF3 | 96 km | 43.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: NEAL SMITH WUI 2016 1 (1,050 acres, 2016).
| Year | Name | Acres Burned | Distance |
| 2016 | NEAL SMITH WUI 2016 1 | 1,050 | 55 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 21°F (-6°C) | 1.5 in | Coldest, Driest |
| February | 27°F (-3°C) | 1.6 in | |
| March | 39°F (4°C) | 2.9 in | |
| April | 51°F (10°C) | 3.5 in | |
| May | 61°F (16°C) | 4.1 in | |
| June | 71°F (21°C) | 4.5 in | Wettest |
| July | 73°F (23°C) | 4.5 in | |
| August | 73°F (23°C) | 3.8 in | Warmest |
| September | 65°F (18°C) | 4.2 in | |
| October | 53°F (12°C) | 2.9 in | |
| November | 39°F (4°C) | 2.6 in | |
| December | 26°F (-3°C) | 1.9 in |
Williamson has a seasonal temperature swing of 52°F / from 21°F in January to 73°F in August. Total annual precipitation is 38.1 inches, with June being the wettest month (4.5") and January the driest (1.5").