Alton, IL Weather & Climate Normals
What a normal year in Alton actually looks like
On the 30-year record NOAA keeps for Alton, 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 Alton's weather actually swings
Average temperatures in Alton run from 30°F in Jan up to 78°F in Jul, a 47.9°F seasonal swing, one of the widest gaps in this dataset.
Alton, month by month
| Month | Avg high | Avg low | Precip |
|---|---|---|---|
| Jan | 39°F | 22°F | 2.53in |
| Feb | 44°F | 25°F | 2.52in |
| Mar | 54°F | 35°F | 3.46in |
| Apr | 66°F | 45°F | 4.92in |
| May | 75°F | 56°F | 5.46in |
| Jun | 84°F | 66°F | 3.4in |
| Jul | 87°F | 69°F | 3.95in |
| Aug | 86°F | 67°F | 3.3in |
| Sep | 80°F | 60°F | 3.38in |
| Oct | 68°F | 48°F | 2.93in |
| Nov | 54°F | 37°F | 3.43in |
| Dec | 44°F | 27°F | 2.59in |
If you're timing a visit, Apr, May, Jun, Sep, and Oct are Alton's mildest stretch; if you're moving there, you should plan around Jul's heat and Jan's cold instead.
How wet Alton actually gets
Alton averages 41.87in of precipitation a year across roughly 99 days with measurable rain or snow; the nearest NOAA station does not record snowfall, so no snow figure is shown rather than guessed.
Alton against the rest of the country
Out of 4876 cities scored here, Alton comes in at 2107; within IL alone it ranks 13 of 330. Population is about 24,967.
Checking the actual forecast
These figures come from Alton - Melvin Price L&D, IL US, the NOAA station 2.6 miles from Alton, averaged over 30 years, not tomorrow's forecast.
More on how this is worked out
Why some cities show no snow or rain figure · What a 30-year climate normal actually is