Grinnell, IA climate
Grinnell has cold, snowy winters and pleasant summers. A typical July afternoon reaches 84°, a January night drops to 12°, and about 31 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Grinnell feels like
Winter
Spring
Summer
Fall
Grinnell weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 28° | 12° | 1.0" | 9.0" | 8 | 11° – 33° |
| February | 33° | 16° | 1.2" | 9.1" | 8 | 13° – 36° |
| March | 47° | 27° | 2.1" | 3.4" | 9 | 29° – 51° |
| April | 60° | 38° | 3.8" | 0.6" | 12 | 40° – 56° |
| May | 71° | 49° | 5.1" | 0 | 13 | 54° – 68° |
| June | 80° | 59° | 5.6" | 0 | 12 | 67° – 74° |
| July | 84° | 63° | 4.3" | 0 | 9 | 67° – 79° |
| August | 82° | 60° | 4.3" | 0 | 11 | 66° – 77° |
| September | 75° | 52° | 3.7" | 0 | 9 | 58° – 69° |
| October | 62° | 40° | 2.9" | 0.5" | 10 | 46° – 56° |
| November | 47° | 28° | 2.0" | 1.5" | 7 | 29° – 48° |
| December | 34° | 17° | 1.5" | 6.9" | 8 | 10° – 35° |
| Year | 59° | 38° | 37.6" | 31.0" | 115 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Grinnell
Grinnell gets 38 inches of rain and melted snow a year. June is the wettest month and January the driest. Rain or snow falls on about 115 days a year.
About 155 frost-free days a year
In half of years the last 32° night comes by May 3 and the first one by October 6. That leaves about 155 frost-free days for gardens, shorter than 76% of U.S. towns.
Heating and cooling a home in Grinnell
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Grinnell, 91% of that work is heating and 9% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How Grinnell compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Grinnell averaged 0.8° warmer than the 1900s. The biggest change is in December (+2.4°). The shift is smaller than in 87% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Grinnell’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 10° to 35°. June is the most reliable, staying within 7°.
Common questions about Grinnell’s climate
What is the coldest month in Grinnell?
January, with a typical high of 28° and a low of 12°.
What is the hottest month in Grinnell?
July, with a typical high of 84° and a low of 63°. About 11 days a year reach 90°.
How much snow does Grinnell get?
About 31 inches in a normal winter, most of it in February.
When is the first frost in Grinnell?
In half of years the first 32° night comes by October 6, and the last spring frost by May 3.
What is the rainiest month in Grinnell?
June, with 5.6 inches of rain and melted snow. The year totals 38 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Grinnell itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Grinnell 3 Sw, IA (2 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.