Decatur, Illinois vs Upper Alton Climate
99%matchDecatur vs Upper Alton: a 99% climate match. Very close: temperatures within 2°F (1°C), with similar rain, humidity and sun.
Decatur gets 41 in (1034 mm) of rain a year and Upper Alton 40 in (1019 mm). July is the warmest month in both, with highs of 88°F (31°C) in Decatur and 88°F (31°C) in Upper Alton.
Climate fingerprints: ring color = average temperature, thickness = rain. January at the top.
Month by month
Highs and lows (°F)
DecaturUpper Altonsolid = high, dashed = low
Rain (in per month)
DecaturUpper Alton
Monthly averages
| Month | High | Low | Rain | |||
|---|---|---|---|---|---|---|
| Decatur | Upper Alton | Decatur | Upper Alton | Decatur | Upper Alton | |
| Jan | 37°F(3°C) | 39°F(4°C) | 20°F(-7°C) | 21°F(-6°C) | 2.2 in(55 mm) | 2.1 in(54 mm) |
| Feb | 41°F(5°C) | 44°F(7°C) | 23°F(-5°C) | 25°F(-4°C) | 2.0 in(51 mm) | 2.1 in(54 mm) |
| Mar | 53°F(12°C) | 55°F(13°C) | 33°F(1°C) | 35°F(1°C) | 3.0 in(75 mm) | 3.2 in(82 mm) |
| Apr | 65°F(19°C) | 67°F(20°C) | 43°F(6°C) | 45°F(7°C) | 4.1 in(105 mm) | 3.9 in(99 mm) |
| May | 76°F(25°C) | 76°F(25°C) | 53°F(12°C) | 55°F(13°C) | 4.9 in(125 mm) | 4.8 in(121 mm) |
| Jun | 85°F(29°C) | 84°F(29°C) | 62°F(17°C) | 64°F(18°C) | 4.6 in(118 mm) | 4.0 in(102 mm) |
| Jul | 88°F(31°C) | 88°F(31°C) | 66°F(19°C) | 68°F(20°C) | 4.3 in(110 mm) | 4.0 in(102 mm) |
| Aug | 87°F(30°C) | 87°F(30°C) | 64°F(18°C) | 66°F(19°C) | 3.4 in(86 mm) | 3.4 in(86 mm) |
| Sep | 81°F(27°C) | 81°F(27°C) | 56°F(13°C) | 58°F(14°C) | 3.3 in(83 mm) | 3.6 in(92 mm) |
| Oct | 68°F(20°C) | 69°F(20°C) | 45°F(7°C) | 46°F(8°C) | 3.0 in(77 mm) | 3.0 in(75 mm) |
| Nov | 53°F(12°C) | 55°F(13°C) | 34°F(1°C) | 35°F(2°C) | 3.1 in(80 mm) | 3.3 in(83 mm) |
| Dec | 41°F(5°C) | 43°F(6°C) | 25°F(-4°C) | 26°F(-3°C) | 2.7 in(69 mm) | 2.7 in(69 mm) |
1991–2020 averages, by calendar month.