Union, OH Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Montgomery County, Ohio.
This Afternoon
68°F
Rain Likely
Rain likely. Cloudy, with a high near 68. South wind 15 to 18 mph, with gusts as high as 29 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 68°F | Rain Likely | 15 to 18 mph S | 74% |
| Tonight | 49°F | Chance Light Rain then Mostly Cloudy | 7 to 14 mph SW | 44% |
| Thursday | 64°F | Mostly Sunny | 7 to 16 mph SW | 1% |
| Thursday Night | 44°F | Mostly Cloudy | 5 to 9 mph W | 4% |
| Friday | 56°F | Slight Chance Light Rain | 5 to 13 mph NW | 19% |
| Friday Night | 35°F | Mostly Cloudy | 7 to 12 mph NW | 12% |
| Saturday | 53°F | Partly Sunny | 8 to 12 mph NW | 1% |
| Saturday Night | 31°F | Partly Cloudy | 3 to 7 mph NW | 0% |
| Sunday | 57°F | Sunny | 3 to 12 mph W | 1% |
| Sunday Night | 33°F | Mostly Clear | 3 to 9 mph W | 1% |
| Monday | 62°F | Sunny | 3 to 9 mph W | 0% |
| Monday Night | 37°F | Mostly Clear | 8 mph SW | 0% |
| Tuesday | 65°F | Sunny | 9 mph W | 1% |
| Tuesday Night | 36°F | Mostly Clear | 2 to 7 mph NW | 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
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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.