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Weather & Climate in Union, IA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Union 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 37.9 inches. The area receives 33.2 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 929 feet.
Temperature
17°F Jan (-8°C)
73°F Jul (23°C)
| Annual Average | 46.9°F |
| 13% below US avg | |
| January Average | 17°F (-8°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 260 days/yr |
Geography
| Elevation | 929 ft (283 m) |
| Area | 0.6 sq mi (1.4 km²) |
| Population Density | 686/sq mi |
| Coordinates | 42.2435°N, 93.0625°W |
| Timezone | America/Chicago |
| County | Hardin County County |
| Nearest Airport | Waterloo Regional (ALO) 40 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 58.4 / 100 |
| Social Vulnerability | 38.3 / 100 |
| Community Resilience | 80.5 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Relatively High |
| Strong Wind | Relatively Moderate |
| Heat Wave | Very Low |
| Winter Weather | Relatively Moderate |
| 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)
Tornado History
719 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 42 fatalities, 1,156 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 25, 2008 | EF5 | 37 km | 41.0 mi | 9 |
| Jun 13, 1976 | EF5 | 75 km | 21.3 mi | 0 |
| May 15, 1968 | EF5 | 59 km | 62.1 mi | 13 |
| Oct 14, 1966 | EF5 | 78 km | 9.7 mi | 6 |
| May 30, 1989 | EF4 | 10 km | 11.0 mi | 0 |
| May 24, 1989 | EF4 | 62 km | 66.0 mi | 0 |
| Sep 28, 1986 | EF4 | 71 km | 20.0 mi | 0 |
| May 4, 1977 | EF4 | 95 km | 2.0 mi | 0 |
| Aug 12, 1974 | EF4 | 91 km | 2.0 mi | 0 |
| Jun 18, 1974 | EF4 | 73 km | 15.3 mi | 2 |
| Jun 8, 1967 | EF4 | 97 km | 2.0 mi | 0 |
| Aug 26, 1965 | EF4 | 71 km | 4.7 mi | 1 |
| Sep 1, 1961 | EF4 | 60 km | 26.6 mi | 0 |
| May 10, 1953 | EF4 | 99 km | 26.6 mi | 0 |
| Jul 19, 2018 | EF3 | 88 km | 9.2 mi | 0 |
| Jul 19, 2018 | EF3 | 18 km | 8.4 mi | 0 |
| Jun 12, 2013 | EF3 | 87 km | 6.2 mi | 0 |
| May 25, 2008 | EF3 | 94 km | 32.0 mi | 0 |
| Nov 12, 2005 | EF3 | 84 km | 17.6 mi | 1 |
| May 11, 2000 | EF3 | 59 km | 18.6 mi | 1 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
5 wildfires (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 | 76 km |
| 2009 | UNNAMED | 939 | 79 km |
| 2010 | FOLEY | 786 | 82 km |
| 2011 | ACE AUTO | 676 | 92 km |
| 2011 | IRCP WUI ROFAE #2 FY11 | 510 | 72 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 17°F (-8°C) | 0.9 in | Coldest, Driest |
| February | 23°F (-5°C) | 1.0 in | |
| March | 35°F (2°C) | 2.2 in | |
| April | 48°F (9°C) | 3.2 in | |
| May | 60°F (16°C) | 4.2 in | |
| June | 70°F (21°C) | 4.8 in | Wettest |
| July | 73°F (23°C) | 4.3 in | Warmest |
| August | 71°F (22°C) | 4.2 in | |
| September | 63°F (17°C) | 3.5 in | |
| October | 51°F (10°C) | 2.6 in | |
| November | 35°F (2°C) | 1.8 in | |
| December | 22°F (-6°C) | 1.2 in |
Union has a seasonal temperature swing of 56°F / from 17°F in January to 73°F in July. Total annual precipitation is 33.9 inches, with June being the wettest month (4.8") and January the driest (0.9").