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Weather & Climate in Thornton, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Thornton experiences four distinct seasons with an average annual temperature of 47°F (8°C). Winters average 17°F in January while summers reach 73°F in July. The area gets 260 sunny days per year, above the national average. Annual precipitation totals 38.1 inches. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 1,191 feet.
Temperature
17°F Jan (-9°C)
73°F Jul (23°C)
| Annual Average | 46.6°F |
| 14% below US avg | |
| January Average | 17°F (-9°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 1,191 ft (363 m) |
| Area | 1.2 sq mi (3.2 km²) |
| Population Density | 431/sq mi |
| Coordinates | 42.9442°N, 93.3870°W |
| Timezone | America/Chicago |
| County | Franklin County County |
| Nearest Airport | Northeast Iowa Regional (CCY) 40 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 22.0 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 51.7 / 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 | Very Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Relatively Low |
| Drought | Relatively High |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
2 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M2.8.
| Apr 25, 2017 | Near Mankato, Minnesota | M2.8 | 147 km | 0 km |
| Jun 30, 2021 | 4 km E of Rembrandt, Iowa | M2.7 | 141 km | 10 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
644 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 55 fatalities, 1,061 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 25, 2008 | EF5 | 60 km | 41.0 mi | 9 |
| May 15, 1968 | EF5 | 29 km | 62.1 mi | 13 |
| Oct 14, 1966 | EF5 | 27 km | 9.7 mi | 6 |
| Jun 17, 2010 | EF4 | 73 km | 16.9 mi | 1 |
| May 30, 1989 | EF4 | 76 km | 11.0 mi | 0 |
| May 24, 1989 | EF4 | 87 km | 66.0 mi | 0 |
| May 4, 1977 | EF4 | 78 km | 2.0 mi | 0 |
| Jul 12, 1971 | EF4 | 83 km | 10.9 mi | 0 |
| Jun 8, 1967 | EF4 | 80 km | 2.0 mi | 0 |
| Apr 30, 1967 | EF4 | 96 km | 20.1 mi | 6 |
| Apr 30, 1967 | EF4 | 70 km | 38.7 mi | 5 |
| Apr 30, 1967 | EF4 | 59 km | 7.6 mi | 0 |
| Apr 30, 1967 | EF4 | 43 km | 13.3 mi | 0 |
| May 5, 1965 | EF4 | 59 km | 41.6 mi | 0 |
| Aug 29, 1964 | EF4 | 69 km | 15.8 mi | 0 |
| Sep 1, 1961 | EF4 | 36 km | 26.6 mi | 0 |
| May 10, 1953 | EF4 | 98 km | 162.0 mi | 2 |
| May 10, 1953 | EF4 | 18 km | 26.6 mi | 0 |
| Jun 12, 2013 | EF3 | 25 km | 6.2 mi | 0 |
| Jun 17, 2010 | EF3 | 84 km | 18.2 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 17°F (-9°C) | 0.8 in | Coldest, Driest |
| February | 21°F (-6°C) | 0.9 in | |
| March | 33°F (0°C) | 2.0 in | |
| April | 46°F (8°C) | 3.2 in | |
| May | 59°F (15°C) | 4.1 in | |
| June | 69°F (21°C) | 4.8 in | Wettest |
| July | 73°F (23°C) | 4.5 in | Warmest |
| August | 70°F (21°C) | 4.0 in | |
| September | 62°F (17°C) | 3.7 in | |
| October | 50°F (10°C) | 2.5 in | |
| November | 34°F (1°C) | 1.7 in | |
| December | 20°F (-7°C) | 1.1 in |
Thornton has a seasonal temperature swing of 56°F / from 17°F in January to 73°F in July. Total annual precipitation is 33.2 inches, with June being the wettest month (4.8") and January the driest (0.8").