Glen Carbon has chilly winters and warm summers
A typical July afternoon reaches 88°, a January night drops to 23°, and about 11 inches of snow falls in a normal winter.
A year in Glen Carbon at a glance
Each month’s typical high and low, and what it brings.
What stands out about Glen Carbon’s climate
Read from where Glen Carbon sits among Illinois’s towns. The page puts what stands out first.
Living with Glen Carbon’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
214 frost-free days. The last frost comes by Apr 4 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 5.
About 11" a winter over 4 days with an inch or more, most in January. Snow covers the ground about 15 days a year.
Months averaging under 55° run from November through March. Heating is 77% of the year’s heating-and-cooling load.
About 29 days a year reach 90°, and July afternoons average 88°.
The nicest months are April, May, September and October. 0.7 miles of trails are waiting.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →About 214 frost-free days a year
In half of years the last 32° night comes by April 4 and the first by November 5.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
What a year in Glen Carbon feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
11 inches of snow, 43 of rain and melt
May is the wettest month and February the driest. Rain or snow falls on about 112 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Glen Carbon and its neighbors
Edwardsville has the coldest January nights next door (23°) and Pontoon Beach the hottest July afternoons (89°). Tap a town to see its climate.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Glen Carbon averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.2°).
A smaller shift than in 70% of U.S. towns.
Change by month
How Glen Carbon compares
Against every U.S. town on TownTapestry, each counted once, with its place in Illinois.
Glen Carbon 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 | 39° | 23° | 2.6" | 3.7" | 8 | 6 | 26° – 42° |
| February | 44° | 27° | 2.3" | 2.5" | 8 | 3 | 26° – 45° |
| March | 55° | 36° | 3.4" | 1.0" | 11 | 1 | 38° – 59° |
| April | 67° | 45° | 4.8" | 0.1" | 11 | 0 | 48° – 62° |
| May | 76° | 56° | 5.0" | 0 | 13 | 0 | 61° – 73° |
| June | 85° | 65° | 4.3" | 0 | 10 | 0 | 70° – 79° |
| July | 88° | 68° | 4.3" | 0 | 8 | 0 | 73° – 85° |
| August | 87° | 66° | 3.4" | 0 | 9 | 0 | 71° – 82° |
| September | 80° | 58° | 3.4" | 0 | 8 | 0 | 64° – 75° |
| October | 69° | 47° | 3.3" | 0 | 9 | 0 | 53° – 64° |
| November | 55° | 36° | 3.5" | 0.2" | 9 | 0 | 38° – 53° |
| December | 43° | 28° | 2.7" | 3.3" | 8 | 4 | 21° – 44° |
| Year | 66° | 46° | 42.8" | 10.8" | 112 | 15 |
Heating and cooling a home in Glen Carbon
77% of the work is heating.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. Source: NOAA station normals.
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 21° to 44°. June is the most reliable, staying within 9°.
Common questions about Glen Carbon’s climate
What is the coldest month in Glen Carbon?
January, with a typical high of 39° and a low of 23°.
What is the hottest month in Glen Carbon?
July, with a typical high of 88° and a low of 68°. About 29 days a year reach 90°.
How much snow does Glen Carbon get?
About 11 inches in a normal winter, most of it in January.
When is the first frost in Glen Carbon?
In half of years the first 32° night comes by November 5, and the last spring frost by April 4.
What is the rainiest month in Glen Carbon?
May, with 5.0 inches of rain and melted snow. The year totals 43 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in Glen Carbon.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for Glen Carbon itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Edwardsville 2 W, IL (4 mi, snow) and Alton - Melvin Price L&d, IL (12 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. Today’s forecast: National Weather Service.