Union, OH Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Montgomery County, Ohio.
Overnight
62°F
Light Rain
Rain. Cloudy, with a low around 62. South wind around 17 mph, with gusts as high as 29 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 62°F | Light Rain | 17 mph S | 83% |
| Wednesday | 66°F | Rain | 14 to 20 mph S | 97% |
| Wednesday Night | 49°F | Chance Light Rain then Mostly Cloudy | 7 to 13 mph SW | 42% |
| Thursday | 63°F | Mostly Sunny | 7 to 15 mph SW | 0% |
| Thursday Night | 45°F | Mostly Cloudy | 3 to 9 mph SW | 8% |
| Friday | 57°F | Chance Light Rain | 3 to 12 mph W | 37% |
| Friday Night | 37°F | Chance Light Rain then Mostly Cloudy | 8 to 12 mph NW | 30% |
| Saturday | 54°F | Partly Sunny | 10 mph NW | 3% |
| Saturday Night | 33°F | Partly Cloudy | 3 to 7 mph W | 3% |
| Sunday | 57°F | Sunny | 3 to 12 mph W | 3% |
| Sunday Night | 33°F | Mostly Clear | 5 to 9 mph W | 3% |
| Monday | 59°F | Sunny | 5 to 9 mph W | 2% |
| Monday Night | 37°F | Mostly Clear | 8 mph SW | 2% |
| Tuesday | 64°F | Sunny | 7 to 10 mph W | 1% |
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.