Union, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Hardin County, Iowa.
This Afternoon
67°F
Showers And Thunderstorms Likely
Showers and thunderstorms likely. Cloudy. High near 67, with temperatures falling to around 63 in the afternoon. West wind around 7 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 67°F | Showers And Thunderstorms Likely | 7 mph W | 73% |
| Tonight | 46°F | Showers And Thunderstorms | 6 to 10 mph NW | 83% |
| Wednesday | 52°F | Chance Rain Showers | 10 to 17 mph W | 42% |
| Wednesday Night | 42°F | Cloudy then Chance Rain Showers | 9 to 13 mph W | 47% |
| Thursday | 52°F | Rain Showers Likely | 12 mph NW | 64% |
| Thursday Night | 38°F | Slight Chance Rain Showers then Mostly Cloudy | 6 to 9 mph N | 18% |
| Friday | 51°F | Partly Sunny | 3 to 7 mph N | 3% |
| Friday Night | 31°F | Partly Cloudy | 2 mph NNE | 0% |
| Saturday | 55°F | Mostly Sunny | 0 to 3 mph W | 1% |
| Saturday Night | 35°F | Mostly Clear | 3 mph W | 4% |
| Sunday | 60°F | Sunny | 6 mph WNW | 6% |
| Sunday Night | 37°F | Mostly Clear | 5 mph SW | 2% |
| Monday | 64°F | Sunny | 5 to 12 mph SW | 0% |
| Monday Night | 39°F | Mostly Clear | 5 mph WNW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Union (42.244, -93.062). Updated through the day.
Growing snapshot for Union
Last spring frost
Apr 27
First fall frost
Oct 10
Growing season
165 days
Hardiness zone
5a
More local growing data for Union: nearby ZIP 50258 weather · frost dates · planting calendar · Iowa frost dates
Nearby towns & communities
Alden
Buckeye
Eldora
Garden City
Hubbard
Iowa Falls
New Providence
Owasa
Radcliffe
Steamboat Rock
Whitten
Climate data from the nearest NOAA station, Eldora, Ia (9.8 mi from Union). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 3, 2026.