Collinsville, IL Weather & Climate Normals
What a normal year in Collinsville actually looks like
On the 30-year record NOAA keeps for Collinsville, IL, the comfort score comes out to 44/100, strongly seasonal: Comfortable weather is limited to a shorter window; summers, winters, or precipitation swing wide. Only 4 months a year land in the 55–75°F range this site treats as mild.
How much Collinsville's weather actually swings
Average temperatures in Collinsville run from 32°F in Jan up to 79°F in Jul, a 46.7°F seasonal swing, one of the widest gaps in this dataset.
Collinsville, month by month
| Month | Avg high | Avg low | Precip |
|---|---|---|---|
| Jan | 40°F | 24°F | 2.46in |
| Feb | 46°F | 28°F | 1.96in |
| Mar | 56°F | 36°F | 3.27in |
| Apr | 68°F | 46°F | 4.48in |
| May | 77°F | 57°F | 4.84in |
| Jun | 86°F | 65°F | 4.36in |
| Jul | 89°F | 69°F | 3.7in |
| Aug | 88°F | 66°F | 3.68in |
| Sep | 81°F | 57°F | 3.36in |
| Oct | 69°F | 46°F | 3.07in |
| Nov | 55°F | 36°F | 3.34in |
| Dec | 44°F | 29°F | 2.32in |
If you're timing a visit, Apr, May, Sep, and Oct are Collinsville's mildest stretch; if you're moving there, you should plan around Jul's heat and Jan's cold instead.
How wet Collinsville actually gets
Collinsville averages 40.84in of precipitation a year across roughly 117 days with measurable rain or snow; the nearest NOAA station does not record snowfall, so no snow figure is shown rather than guessed.
Collinsville against the rest of the country
Out of 4876 cities scored here, Collinsville comes in at 3750; within IL alone it ranks 189 of 330. Population is about 23,766.
Checking the actual forecast
These figures come from Cahokia St Louis Ap, IL US, the NOAA station 10.9 miles from Collinsville, averaged over 30 years, not tomorrow's forecast.
More on how this is worked out
Why some cities show no snow or rain figure · Why this uses the nearest NOAA station