Grinnell, Iowa Weather
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Climate of Grinnell: monthly averages
Based on 25 years of satellite and reanalysis data (2001-2025), July is usually the hottest month in Grinnell, with average daytime highs around 30°C. January is the coolest, when nights typically fall to about -10°C and frost is possible on the coldest nights. That is a wide yearly range of roughly 40°C, so the seasons feel very different from each other.
The area receives about 910 mm of rain in a typical year. Most of it falls from May to June and August, and June is the wettest month at roughly 134 mm.
For outdoor plans and travel, July and September usually offer the most comfortable weather in Grinnell, with mild days and relatively little rain.
| Month | Avg high | Avg low | Rainfall | Humidity |
|---|---|---|---|---|
| Jan | -1° | -10° | 26 mm | 84% |
| Feb | 1° | -9° | 34 mm | 82% |
| Mar | 9° | -3° | 52 mm | 77% |
| Apr | 17° | 4° | 91 mm | 73% |
| May | 22° | 11° | 114 mm | 75% |
| Jun | 28° | 17° | 134 mm | 75% |
| Jul | 30° | 19° | 94 mm | 72% |
| Aug | 29° | 17° | 112 mm | 71% |
| Sep | 25° | 13° | 87 mm | 71% |
| Oct | 17° | 5° | 74 mm | 73% |
| Nov | 9° | -1° | 47 mm | 78% |
| Dec | 1° | -7° | 43 mm | 85% |
Source: NASA POWER (MERRA-2 reanalysis), averaged over the roughly 50 km grid area around Grinnell. Values describe typical conditions, not a forecast.
About Grinnell weather
Grinnell is one of many towns in Iowa's humid continental climate, typical of the US corn belt, about 77 km east of Des Moines. Before the rains arrive, there's warm, humid summers (June–August). Cooler months mean cold winters (December–February) with regular snow. This page shows live, auto-refreshing weather for Grinnell: current conditions, an hourly breakdown, a 16-day outlook, a date-lookup tool for any past or future date, and real-time air quality, sourced from Open-Meteo. Local timezone: America/Chicago.
Frequently asked questions
Grinnell is about 77 km east of Des Moines, in Iowa.
Grinnell sees cold winters (December–February) with regular snow.
The live current conditions, hourly forecast and 16-day outlook above are pulled in real time for Grinnell's exact coordinates. No fixed schedule, the page updates whenever you load it.
July is usually the hottest month in Grinnell, with average daytime highs of about 30°C and nights around 19°C.
The coldest nights come in January, when the average low is about -10°C and daytime highs reach around -1°C. Frost is possible on clear, calm nights.
Grinnell receives about 910 mm of rain in a typical year. June is the wettest month at roughly 134 mm, and the main rainy period is May to June and August.
July and September usually offer the most comfortable weather in Grinnell, with mild daytime temperatures and little rain.
In November Grinnell typically sees daytime highs near 9°C and lows near -1°C, with about 47 mm of rain over the month and average humidity around 78%. Check the live forecast above for this week's actual conditions.
Up to 16 days ahead using the extended forecast and date picker above; further-out or historical dates use the same date lookup tool.
Live temperature for Grinnell is shown at the top of this page and refreshes automatically — see the hourly breakdown below for how it changes through the day.
Grinnell's day-to-day weather follows the broader pattern of Iowa described above. See the hourly weather forecast or the air quality index for more detail.