Union, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union, a city in Hardin County, Iowa.
Overnight
67°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Mostly cloudy, with a low around 67. South southeast wind around 6 mph. Chance of precipitation is 40%. New rainfall amounts between a quarter and half of an inch possible.
7-day forecast for Union
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 67°F | Chance Showers And Thunderstorms | 6 mph SSE | 41% |
| Saturday | 79°F | Showers And Thunderstorms Likely | 8 mph WSW | 57% |
| Saturday Night | 60°F | Chance Showers And Thunderstorms | 9 mph N | 33% |
| Sunday | 66°F | Chance Rain Showers | 10 to 14 mph NE | 32% |
| Sunday Night | 54°F | Chance Rain Showers | 13 mph ENE | 43% |
| Monday | 62°F | Chance Rain Showers | 13 mph NE | 44% |
| Monday Night | 49°F | Chance Rain Showers | 6 to 10 mph NE | 44% |
| Tuesday | 61°F | Slight Chance Rain Showers then Partly Sunny | 8 mph ENE | 15% |
| Tuesday Night | 45°F | Partly Cloudy | 2 to 6 mph ENE | 2% |
| Wednesday | 66°F | Sunny | 5 mph ENE | 1% |
| Wednesday Night | 50°F | Partly Cloudy | 3 mph E | 5% |
| Thursday | 67°F | Partly Sunny | 3 mph ESE | 13% |
| Thursday Night | 53°F | Mostly Cloudy | 2 mph E | 10% |
| Friday | 69°F | Partly Sunny | 1 to 5 mph ESE | 6% |
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 Sep 19, 2026.