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

When	Temp	Forecast	Wind	Precip
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

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.