Grinnell, IA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Grinnell, a city in Poweshiek County, Iowa.
Today
83°F
Partly Sunny then Chance Showers And Thunderstorms
A chance of showers and thunderstorms after noon. Partly sunny. High near 83, with temperatures falling to around 80 in the afternoon. West northwest wind around 7 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 |
|---|---|---|---|---|
| Today | 83°F | Partly Sunny then Chance Showers And Thunderstorms | 7 mph WNW | 27% |
| Tonight | 61°F | Showers And Thunderstorms | 9 mph NNE | 87% |
| Wednesday | 74°F | Showers And Thunderstorms | 7 mph NNE | 84% |
| Wednesday Night | 56°F | Chance Showers And Thunderstorms | 3 mph NNE | 46% |
| Thursday | 80°F | Sunny | 2 mph ENE | 4% |
| Thursday Night | 59°F | Mostly Clear | 1 mph ESE | 0% |
| Friday | 83°F | Sunny | 5 mph SSE | 6% |
| Friday Night | 65°F | Mostly Clear | 5 mph SSE | 14% |
| Saturday | 87°F | Sunny then Slight Chance Rain Showers | 3 to 7 mph S | 15% |
| Saturday Night | 70°F | Slight Chance Rain Showers then Slight Chance Showers And Thunderstorms | 6 to 9 mph S | 15% |
| Sunday | 88°F | Slight Chance Showers And Thunderstorms then Sunny | 9 mph S | 15% |
| Sunday Night | 69°F | Chance Showers And Thunderstorms | 8 mph S | 34% |
| Monday | 87°F | Chance Showers And Thunderstorms | 10 mph S | 34% |
| Monday Night | 69°F | Chance Showers And Thunderstorms | 12 mph E | 29% |
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 Aug 4, 2026.