Union, OH Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Montgomery County, Ohio.
Tonight
62°F
Mostly Cloudy then Rain Showers Likely
Rain showers likely after 2am. Mostly cloudy, with a low around 62. Southeast wind 12 to 17 mph. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 62°F | Mostly Cloudy then Rain Showers Likely | 12 to 17 mph SE | 62% |
| Wednesday | 68°F | Showers And Thunderstorms | 14 to 20 mph S | 98% |
| Wednesday Night | 50°F | Slight Chance Rain Showers then Mostly Cloudy | 6 to 13 mph SW | 24% |
| Thursday | 65°F | Mostly Sunny | 7 to 15 mph SW | 0% |
| Thursday Night | 45°F | Partly Cloudy | 2 to 9 mph W | 1% |
| Friday | 60°F | Partly Sunny | 2 to 9 mph NW | 12% |
| Friday Night | 39°F | Partly Cloudy | 9 mph NW | 12% |
| Saturday | 55°F | Slight Chance Light Rain | 9 mph NW | 19% |
| Saturday Night | 34°F | Partly Cloudy | 2 to 6 mph W | 9% |
| Sunday | 57°F | Mostly Sunny | 2 to 12 mph W | 13% |
| Sunday Night | 34°F | Partly Cloudy | 6 to 10 mph W | 13% |
| Monday | 60°F | Slight Chance Light Rain | 6 to 12 mph W | 15% |
| Monday Night | 38°F | Mostly Clear | 10 mph SW | 12% |
| Tuesday | 64°F | Sunny | 8 to 12 mph W | 3% |
Forecast source: National Weather Service (api.weather.gov) for Union (39.907, -84.293). Updated through the day.
Growing snapshot for Union
Last spring frost
Apr 16
First fall frost
Oct 28
Growing season
194 days
Hardiness zone
6a
More local growing data for Union: nearby ZIP 45322 weather · frost dates · planting calendar · Ohio frost dates
Nearby towns & communities
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Miamisburg
Moraine
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Vandalia
West Carrollton
Climate data from the nearest NOAA station, Dayton Intl Ap, Oh (5.8 mi from Union). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.