Union, OH Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Montgomery County, Ohio.
Today
83°F
Sunny
Sunny, with a high near 83. Northeast wind around 3 mph.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 83°F | Sunny | 3 mph NE | 0% |
| Tonight | 63°F | Mostly Clear | 2 mph N | 1% |
| Wednesday | 86°F | Sunny | 0 to 5 mph NW | 7% |
| Wednesday Night | 66°F | Partly Cloudy | 1 to 5 mph W | 3% |
| Thursday | 86°F | Mostly Sunny then Chance Showers And Thunderstorms | 2 to 8 mph SW | 46% |
| Thursday Night | 67°F | Chance Showers And Thunderstorms then Showers And Thunderstorms Likely | 3 to 7 mph SW | 70% |
| Friday | 84°F | Showers And Thunderstorms Likely | 3 to 8 mph SW | 70% |
| Friday Night | 66°F | Showers And Thunderstorms Likely | 6 mph SW | 62% |
| Saturday | 85°F | Chance Showers And Thunderstorms | 3 to 8 mph SW | 30% |
| Saturday Night | 67°F | Chance Showers And Thunderstorms then Partly Cloudy | 3 to 7 mph SW | 30% |
| Sunday | 87°F | Mostly Sunny then Slight Chance Showers And Thunderstorms | 5 to 10 mph SW | 18% |
| Sunday Night | 69°F | Slight Chance Showers And Thunderstorms | 6 to 9 mph SW | 19% |
| Monday | 88°F | Chance Showers And Thunderstorms | 8 to 13 mph SW | 27% |
| Monday Night | 69°F | Chance Showers And Thunderstorms | 6 to 9 mph SW | 34% |
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 Aug 4, 2026.