Chatham, IL Weather & Climate Normals
What a normal year in Chatham actually looks like
On the 30-year record NOAA keeps for Chatham, IL, the comfort score comes out to 49/100, strongly seasonal: Comfortable weather is limited to a shorter window; summers, winters, or precipitation swing wide. Only 5 months a year land in the 55–75°F range this site treats as mild.
How much Chatham's weather actually swings
Average temperatures in Chatham run from 27°F in Jan up to 76°F in Jul, a 48.5°F seasonal swing, one of the widest gaps in this dataset.
Chatham, month by month
| Month | Avg high | Avg low | Precip |
|---|---|---|---|
| Jan | 36°F | 19°F | 2.19in |
| Feb | 41°F | 22°F | 2.2in |
| Mar | 52°F | 31°F | 2.96in |
| Apr | 65°F | 41°F | 4.13in |
| May | 74°F | 53°F | 5.14in |
| Jun | 83°F | 63°F | 5.04in |
| Jul | 86°F | 66°F | 4.38in |
| Aug | 84°F | 64°F | 2.86in |
| Sep | 78°F | 56°F | 3.06in |
| Oct | 66°F | 44°F | 3.1in |
| Nov | 53°F | 33°F | 3.1in |
| Dec | 41°F | 24°F | 2.29in |
If you're timing a visit, May, Jun, Aug, Sep, and Oct are Chatham's mildest stretch; if you're moving there, you should plan around Jul's heat and Jan's cold instead.
How wet Chatham actually gets
Chatham averages 40.45in of precipitation a year across roughly 119 days with measurable rain or snow; the nearest NOAA station does not record snowfall, so no snow figure is shown rather than guessed.
Chatham against the rest of the country
Out of 4876 cities scored here, Chatham comes in at 2151; within IL alone it ranks 16 of 330. Population is about 14,639.
Checking the actual forecast
These figures come from Springfield #2, IL US, the NOAA station 8.5 miles from Chatham, 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