Grinnell, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Grinnell, a city in Poweshiek County, Iowa.
Tonight
46°F
Cloudy then Chance Rain Showers
A chance of rain showers between midnight and 3am. Cloudy. Low around 46, with temperatures rising to around 49 overnight. Southwest wind 8 to 12 mph, with gusts as high as 18 mph. Chance of precipitation is 30%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Grinnell
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 46°F | Cloudy then Chance Rain Showers | 8 to 12 mph SW | 26% |
| Wednesday | 53°F | Chance Rain Showers | 14 mph W | 31% |
| Wednesday Night | 42°F | Mostly Cloudy then Slight Chance Rain Showers | 12 mph WSW | 20% |
| Thursday | 53°F | Chance Rain Showers | 10 mph WNW | 53% |
| Thursday Night | 39°F | Slight Chance Rain Showers then Mostly Cloudy | 8 mph NNW | 16% |
| Friday | 51°F | Partly Sunny | 3 to 8 mph N | 4% |
| Friday Night | 32°F | Partly Cloudy | 2 mph NNW | 0% |
| Saturday | 54°F | Mostly Sunny | 3 mph WSW | 1% |
| Saturday Night | 35°F | Mostly Clear | 5 mph W | 4% |
| Sunday | 60°F | Sunny | 6 mph WNW | 5% |
| Sunday Night | 37°F | Mostly Clear | 6 mph SW | 2% |
| Monday | 64°F | Sunny | 6 to 9 mph SW | 0% |
| Monday Night | 40°F | Mostly Clear | 5 mph WNW | 0% |
| Tuesday | 63°F | Sunny | 5 mph NW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Grinnell (41.735, -92.725). Updated through the day.
Growing snapshot for Grinnell
Last spring frost
May 3
First fall frost
Oct 6
Growing season
155 days
Hardiness zone
5b
More local growing data for Grinnell: nearby ZIP 50112 weather · frost dates · planting calendar · Iowa frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Grinnell 3 Sw, Ia (2.1 mi from Grinnell). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.