Somonauk, IL climate
Somonauk has cold winters and pleasant summers. A typical July afternoon reaches 84°, a January night drops to 15°, and about 30 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Somonauk feels like
Winter
Spring
Summer
Fall
Somonauk 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 | 30° | 15° | 1.7" | 10.2" | 8 | 14° – 34° |
| February | 35° | 19° | 1.6" | 7.1" | 7 | 14° – 38° |
| March | 47° | 28° | 2.3" | 3.4" | 8 | 29° – 53° |
| April | 61° | 38° | 3.7" | 0.3" | 10 | 40° – 56° |
| May | 72° | 49° | 4.7" | 0 | 12 | 54° – 67° |
| June | 81° | 59° | 4.6" | 0 | 11 | 66° – 74° |
| July | 84° | 63° | 3.9" | 0 | 9 | 68° – 80° |
| August | 82° | 61° | 3.8" | 0 | 8 | 66° – 78° |
| September | 76° | 53° | 3.4" | 0 | 8 | 60° – 69° |
| October | 64° | 42° | 3.2" | 0 | 9 | 48° – 58° |
| November | 48° | 31° | 2.4" | 0.5" | 7 | 32° – 49° |
| December | 36° | 20° | 2.0" | 8.3" | 9 | 14° – 39° |
| Year | 60° | 40° | 37.3" | 29.8" | 108 |
“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 Somonauk
Somonauk gets 37 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 108 days a year.
About 166 frost-free days a year
In half of years the last 32° night comes by April 28 and the first one by October 13. That leaves about 166 frost-free days for gardens, shorter than 64% of U.S. towns.
Heating and cooling a home in Somonauk
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Somonauk, 89% of that work is heating and 11% 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.
Somonauk and its neighbors
Somonauk borders 2 towns with climate data. January nights across them vary by 0.1°. Sandwich has the coldest January nights (15°) and Lake Holiday the hottest July afternoons (84°). Somonauk’s January low is 15° and its July high 84°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Somonauk 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 Somonauk averaged 1.2° warmer than the 1900s. The biggest change is in December (+2.4°). The shift is smaller than in 55% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Somonauk’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 14° to 39°. June is the most reliable, staying within 8°.
Common questions about Somonauk’s climate
What is the coldest month in Somonauk?
January, with a typical high of 30° and a low of 15°.
What is the hottest month in Somonauk?
July, with a typical high of 84° and a low of 63°. About 16 days a year reach 90°.
How much snow does Somonauk get?
About 30 inches in a normal winter, most of it in January.
When is the first frost in Somonauk?
In half of years the first 32° night comes by October 13, and the last spring frost by April 28.
What is the rainiest month in Somonauk?
May, with 4.7 inches of rain and melted snow. The year totals 37 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Somonauk itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Shabbona 3s, IL (11 mi, snow) and Chicago Aurora Municipal Airport, IL (14 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.