Union, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Hardin County, Iowa.
Today
80°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Mostly cloudy. High near 80, with temperatures falling to around 76 in the afternoon. West northwest wind around 8 mph. Chance of precipitation is 40%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 80°F | Chance Showers And Thunderstorms | 8 mph WNW | 41% |
| Tonight | 60°F | Showers And Thunderstorms | 5 to 8 mph N | 81% |
| Wednesday | 74°F | Chance Showers And Thunderstorms | 6 mph NE | 41% |
| Wednesday Night | 54°F | Slight Chance Rain Showers | 3 mph NNE | 17% |
| Thursday | 80°F | Sunny | 2 mph ENE | 1% |
| Thursday Night | 59°F | Mostly Clear | 2 mph SSE | 0% |
| Friday | 84°F | Sunny | 1 to 8 mph SSE | 8% |
| Friday Night | 65°F | Mostly Clear | 3 to 7 mph S | 13% |
| Saturday | 87°F | Sunny | 2 to 8 mph S | 13% |
| Saturday Night | 70°F | Mostly Clear then Slight Chance Showers And Thunderstorms | 10 mph SSW | 15% |
| Sunday | 88°F | Slight Chance Showers And Thunderstorms then Mostly Sunny | 9 mph SSE | 15% |
| Sunday Night | 69°F | Chance Showers And Thunderstorms | 8 mph SSE | 34% |
| Monday | 87°F | Chance Showers And Thunderstorms then Slight Chance Showers And Thunderstorms | 7 to 10 mph S | 34% |
| Monday Night | 69°F | Mostly Cloudy then Chance Showers And Thunderstorms | 7 to 10 mph E | 32% |
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 Aug 4, 2026.