Grinnell, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Grinnell, a city in Poweshiek County, Iowa.
Overnight
67°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms. Mostly cloudy, with a low around 67. Southeast wind around 9 mph. Chance of precipitation is 50%. New rainfall amounts between a quarter and half of an inch possible.
7-day forecast for Grinnell
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 67°F | Chance Showers And Thunderstorms | 9 mph SE | 54% |
| Saturday | 81°F | Chance Showers And Thunderstorms | 9 mph SSW | 50% |
| Saturday Night | 61°F | Chance Showers And Thunderstorms | 5 to 8 mph N | 45% |
| Sunday | 66°F | Showers And Thunderstorms Likely | 9 to 13 mph NNE | 65% |
| Sunday Night | 55°F | Showers And Thunderstorms Likely | 13 mph ENE | 65% |
| Monday | 61°F | Rain Showers Likely | 13 mph ENE | 61% |
| Monday Night | 50°F | Rain Showers Likely | 10 mph NE | 61% |
| Tuesday | 59°F | Slight Chance Rain Showers | 9 mph NE | 22% |
| Tuesday Night | 46°F | Partly Cloudy | 6 mph NE | 4% |
| Wednesday | 64°F | Mostly Sunny | 5 mph ENE | 1% |
| Wednesday Night | 50°F | Partly Cloudy | 2 mph E | 3% |
| Thursday | 66°F | Partly Sunny | 3 mph ESE | 11% |
| Thursday Night | 53°F | Partly Cloudy | 2 mph E | 9% |
| Friday | 67°F | Mostly Sunny | 5 mph E | 9% |
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 Sep 19, 2026.