Rock Grove, IL climate
Rock Grove has cold, snowy winters and pleasant summers. A typical July afternoon reaches 83°, a January night drops to 12°, and about 37 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Rock Grove feels like
Winter
Spring
Summer
Fall
Rock Grove 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 | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 28° | 12° | 1.6" | 10.3" | 10 | 22 | 10° – 33° |
| February | 33° | 16° | 1.6" | 9.3" | 8 | 20 | 11° – 36° |
| March | 45° | 26° | 2.3" | 4.5" | 10 | 8 | 27° – 51° |
| April | 59° | 36° | 3.7" | 0.9" | 12 | 1 | 39° – 54° |
| May | 70° | 48° | 4.2" | 0.1" | 13 | 0 | 53° – 65° |
| June | 80° | 58° | 5.6" | 0 | 12 | 0 | 65° – 74° |
| July | 83° | 62° | 4.1" | 0 | 10 | 0 | 66° – 80° |
| August | 81° | 59° | 4.3" | 0 | 10 | 0 | 64° – 76° |
| September | 74° | 52° | 3.8" | 0 | 9 | 0 | 57° – 68° |
| October | 61° | 40° | 3.0" | 0.3" | 10 | 0 | 46° – 57° |
| November | 46° | 29° | 2.4" | 2.2" | 9 | 1 | 29° – 47° |
| December | 33° | 19° | 2.0" | 9.7" | 10 | 12 | 12° – 37° |
| Year | 58° | 38° | 38.4" | 37.3" | 122 | 63 |
“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 Rock Grove
Rock Grove 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 122 days a year. Snow covers the ground about 63 days of the year.
About 165 frost-free days a year
In half of years the last 32° night comes by April 29 and the first one by October 12. That leaves about 165 frost-free days for gardens, shorter than 65% of U.S. towns.
Heating and cooling a home in Rock Grove
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Rock Grove, 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.
Rock Grove and its neighbors
Rock Grove borders 7 towns with climate data. January nights across them vary by 0.7°. Oneco has the coldest January nights (12°) and Laona the hottest July afternoons (83°). Rock Grove’s January low is 12° and its July high 83°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Rock Grove 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 Rock Grove averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.7°). The shift is larger than in 58% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Rock Grove’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 12° to 37°. June is the most reliable, staying within 8°.
Common questions about Rock Grove’s climate
What is the coldest month in Rock Grove?
January, with a typical high of 28° and a low of 12°.
What is the hottest month in Rock Grove?
July, with a typical high of 83° and a low of 62°. About 12 days a year reach 90°.
How much snow does Rock Grove get?
About 37 inches in a normal winter, most of it in January.
When is the first frost in Rock Grove?
In half of years the first 32° night comes by October 12, and the last spring frost by April 29.
What is the rainiest month in Rock Grove?
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 Rock Grove itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Brodhead WWTP, WI (11 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.