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Weather & Climate in Union, OH

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

Union experiences four distinct seasons with an average annual temperature of 54°F (12°C). Winters average 29°F in January while summers reach 76°F in July. The area gets 293 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 41.3 inches. The area receives 25.0 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 790 feet.

Temperature

29°F Jan (-1°C) 76°F Jul (24°C)
Annual Average53.9°F
0% below US avg
January Average29°F (-1°C)
July Average76°F (24°C)
Sunny Days293 days/yr

Geography

Elevation790 ft (241 m)
Area8.4 sq mi (21.6 km²)
Population Density830/sq mi
Coordinates39.9066°N, 84.2933°W
TimezoneAmerica/New_York
CountyMontgomery County County
Nearest AirportJames M Cox Dayton International (DAY)
4 miles away

Precipitation & Snow

Annual Rainfall 41.3"
9% above US avg
Snowfall 25.0"
Wettest Month (May) 4.17"
Driest Month (Feb) 2.20"

Air Quality

AQI Median43.0
RatingGood

Natural Hazard Risk

Overall RiskRelatively Moderate
Risk Score92.7 / 100
Social Vulnerability46.5 / 100
Community Resilience78.3 / 100

Hazard Breakdown

Tornado Relatively High
Hurricane Very Low
Earthquake Relatively Moderate
Wildfire Very Low
Flood Relatively High
Hail Relatively High
Strong Wind Relatively High
Heat Wave Relatively Moderate
Winter Weather Relatively High
Lightning Relatively High
Ice Storm Very High
Drought Very Low
Cold Wave Relatively High
Landslide Relatively Low
Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

10 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.8.

Sep 12, 2004 4 km NW of Manilla, Indiana M3.8 122 km 2 km
Feb 19, 1995 8 km SSE of Rocky Fork Point, Ohio M3.6 112 km 10 km
Apr 17, 1990 8 km NW of Fort Recovery, Ohio M3.0 78 km 5 km
Apr 4, 1994 2 km WNW of Minster, Ohio M2.9 56 km 5 km
May 12, 2006 2 km E of Lima, Ohio M2.8 94 km 5 km
Mar 17, 1999 2 km NNE of Ripley, Ohio M2.8 133 km 0 km
Jun 12, 2015 6 km NW of Convoy, Ohio M2.6 123 km 5 km
Jul 23, 2013 6 km NNE of Germantown, Kentucky M2.6 137 km 4 km
Jan 30, 2004 2 km S of Rockford, Ohio M2.5 90 km 5 km
Jun 4, 1990 4 km SSE of Van Buren, Ohio M2.5 144 km 5 km
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

508 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 74 fatalities, 2,428 injuries.

Date Rating Distance Path Fatalities
Apr 3, 1974 EF5 37 km 31.3 mi 36
May 27, 2019 EF4 17 km 18.2 mi 0
Sep 20, 2000 EF4 39 km 9.0 mi 1
Apr 9, 1999 EF4 76 km 10.0 mi 4
Feb 18, 1992 EF4 95 km 2.8 mi 0
Jun 2, 1990 EF4 93 km 33.0 mi 0
Apr 3, 1974 EF4 82 km 19.8 mi 2
Apr 3, 1974 EF4 85 km 18.0 mi 1
Apr 23, 1968 EF4 90 km 24.1 mi 1
Apr 11, 1965 EF4 100 km 32.5 mi 13
Apr 11, 1965 EF4 50 km 18.4 mi 3
Mar 14, 2024 EF3 77 km 41.3 mi 1
Mar 14, 2024 EF3 69 km 31.3 mi 3
May 27, 2019 EF3 22 km 9.9 mi 0
May 27, 2019 EF3 79 km 10.8 mi 1
May 27, 2019 EF3 17 km 10.5 mi 0
May 14, 2014 EF3 46 km 8.9 mi 0
Nov 10, 2002 EF3 80 km 9.0 mi 0
Jun 30, 1993 EF3 98 km 15.0 mi 0
Nov 22, 1992 EF3 42 km 20.0 mi 0
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 29°F (-1°C) 2.3 in Coldest
February 30°F (-1°C) 2.2 in Driest
March 40°F (5°C) 3.3 in
April 51°F (10°C) 3.9 in
May 61°F (16°C) 4.2 in Wettest
June 70°F (21°C) 3.8 in
July 76°F (24°C) 3.9 in Warmest
August 72°F (22°C) 3.4 in
September 65°F (19°C) 2.7 in
October 54°F (12°C) 2.7 in
November 42°F (6°C) 3.2 in
December 32°F (-0°C) 2.9 in

Union has a seasonal temperature swing of 47°F / from 29°F in January to 76°F in July. Total annual precipitation is 38.5 inches, with May being the wettest month (4.2") and February the driest (2.2").

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