Chester, IL climate
Chester has chilly winters and warm summers. A typical July afternoon reaches 88°, a January night drops to 24°, and about 12 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decade15° warmer than normal today. The forecast high is 90°, and a typical Sep 30 in Chester peaks around 75°.Live forecast: National Weather Service · Normal: NOAA 1991–2020
What a year in Chester feels like
Winter
Spring
Summer
Fall
Chester 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 | 41° | 24° | 2.7" | 3.7" | 8 | 26° – 43° |
| February | 46° | 27° | 2.7" | 3.7" | 8 | 26° – 46° |
| March | 57° | 36° | 3.8" | 1.1" | 10 | 39° – 59° |
| April | 68° | 45° | 5.1" | 0 | 10 | 49° – 62° |
| May | 77° | 55° | 5.2" | 0 | 11 | 60° – 72° |
| June | 85° | 64° | 4.3" | 0 | 9 | 68° – 80° |
| July | 88° | 68° | 3.8" | 0 | 8 | 73° – 84° |
| August | 87° | 65° | 3.1" | 0 | 8 | 70° – 82° |
| September | 81° | 57° | 2.9" | 0 | 7 | 65° – 76° |
| October | 69° | 46° | 3.2" | 0.1" | 8 | 53° – 63° |
| November | 55° | 36° | 4.0" | 0.5" | 8 | 37° – 52° |
| December | 45° | 28° | 3.0" | 2.9" | 8 | 23° – 46° |
| Year | 67° | 46° | 43.7" | 12.0" | 101 |
“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 Chester
Chester gets 44 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 101 days a year.
About 202 frost-free days a year
In half of years the last 32° night comes by April 8 and the first one by October 30. That leaves about 202 frost-free days for gardens, longer than 73% of U.S. towns.
Heating and cooling a home in Chester
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Chester, 76% of that work is heating and 24% is cooling.
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 Chester 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 Chester averaged 1.0° warmer than the 1900s. The biggest change is in February (+1.9°). The shift is smaller than in 69% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Chester’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 23° to 46°. October is the most reliable, staying within 10°.
Common questions about Chester’s climate
What is the coldest month in Chester?
January, with a typical high of 41° and a low of 24°.
What is the hottest month in Chester?
July, with a typical high of 88° and a low of 68°. About 58 days a year reach 90°.
How much snow does Chester get?
About 12 inches in a normal winter, most of it in January.
When is the first frost in Chester?
In half of years the first 32° night comes by October 30, and the last spring frost by April 8.
What is the rainiest month in Chester?
May, with 5.2 inches of rain and melted snow. The year totals 44 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Chester itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Chester, IL (2 mi, snow) and Kaskaskia Rvr Navigation Lock, IL (8 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.