Harman US

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 before 2am, then showers and thunderstorms likely. Mostly cloudy, with a low around 67. Southeast wind around 6 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

7-day forecast for Union

WhenTempForecastWindPrecip
Overnight 67°F Chance Showers And Thunderstorms 6 mph SE 66%
Saturday 79°F Showers And Thunderstorms Likely 8 mph WSW 56%
Saturday Night 60°F Chance Showers And Thunderstorms 9 mph N 33%
Sunday 66°F Chance Rain Showers 10 to 14 mph NE 49%
Sunday Night 54°F Chance Rain Showers 13 mph ENE 35%
Monday 62°F Chance Rain Showers 13 mph NE 60%
Monday Night 49°F Chance Rain Showers 6 to 10 mph NE 60%
Tuesday 61°F Slight Chance Rain Showers then Partly Sunny 8 mph ENE 24%
Tuesday Night 45°F Partly Cloudy 2 to 6 mph ENE 3%
Wednesday 66°F Sunny 5 mph ENE 1%
Wednesday Night 50°F Partly Cloudy 3 mph E 3%
Thursday 67°F Partly Sunny 3 mph ESE 13%
Thursday Night 53°F Mostly Cloudy 2 mph E 9%
Friday 69°F Partly Sunny 1 to 5 mph ESE 7%

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

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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.