Upper Alton Climate by Month
Upper Alton, Illinois, United States
Hot summers and cold winters, with rain spread through the year.
Hot summers and cold winters, with rain spread through the year: that's Upper Alton's climate in short. Afternoon highs range from 39°F (4°C) in January to 88°F (31°C) in July, and January nights average 21°F (-6°C). About 40 in (1019 mm) of rain falls in a typical year, with no clear rainy season.
- Warmest month
- 88°F(31°C)
- Average high, July
- Coldest nights
- 21°F(-6°C)
- Average low, January
- Rain per year
- 40 in(1019 mm)
- No clear rainy season
- Humidity
- 69%
- Sunniest: July
Best and worst months in Upper Alton
Best for weatherThe most comfortable weather comes in May, September and October, with highs around 75°F (24°C) and about 3.8 in (96 mm) of rain a month.
Least pleasantDecember and January are the least pleasant; January is the coldest, with highs of only 39°F (4°C).
Comfort combines how close the afternoon high is to 75°F (24°C) with how much rain falls and how humid it is. See where the weather is best in May.
Temperature and rain through the year
Highs and lows (°F)
Average highAverage low
Rain (in per month)
Upper Alton weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 39°F(4°C) | 21°F(-6°C) | 2.1 in(54 mm) | 71% | 1.7 |
| FebFebruary | 44°F(7°C) | 25°F(-4°C) | 2.1 in(54 mm) | 74% | 2.7 |
| MarMarch | 55°F(13°C) | 35°F(1°C) | 3.2 in(82 mm) | 69% | 3.8 |
| AprApril | 67°F(20°C) | 45°F(7°C) | 3.9 in(99 mm) | 65% | 4.7 |
| MayMayBest | 76°F(25°C) | 55°F(13°C) | 4.8 in(121 mm) | 69% | 5.4 |
| JunJune | 84°F(29°C) | 64°F(18°C) | 4.0 in(102 mm) | 69% | 6.1 |
| JulJuly | 88°F(31°C) | 68°F(20°C) | 4.0 in(102 mm) | 70% | 6.1 |
| AugAugust | 87°F(30°C) | 66°F(19°C) | 3.4 in(86 mm) | 71% | 5.6 |
| SepSeptemberBest | 81°F(27°C) | 58°F(14°C) | 3.6 in(92 mm) | 66% | 4.7 |
| OctOctoberBest | 69°F(20°C) | 46°F(8°C) | 3.0 in(75 mm) | 62% | 3.2 |
| NovNovember | 55°F(13°C) | 35°F(2°C) | 3.3 in(83 mm) | 69% | 2.1 |
| DecDecember | 43°F(6°C) | 26°F(-3°C) | 2.7 in(69 mm) | 74% | 1.6 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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