DeKalb Climate by Month
DeKalb, Illinois, United States
Warm summers and freezing winters, with rain spread through the year.
DeKalb has warm summers and freezing winters, with rain spread through the year. Expect highs of 84°F (29°C) in July and 30°F (-1°C) in January, with the coldest nights (January) near 14°F (-10°C). About 38 in (961 mm) of rain falls in a typical year, with no clear rainy season.
- Warmest month
- 84°F(29°C)
- Average high, July
- Coldest nights
- 14°F(-10°C)
- Average low, January
- Rain per year
- 38 in(961 mm)
- No clear rainy season
- Humidity
- 74%
- Sunniest: July
Best and worst months in DeKalb
Best for weatherThe most comfortable weather comes in September, with highs around 76°F (25°C) and about 3.7 in (94 mm) of rain a month.
Least pleasantJanuary is the least pleasant month: it's the coldest, with highs of only 30°F (-1°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 September.
Temperature and rain through the year
Highs and lows (°F)
Average highAverage low
Rain (in per month)
DeKalb weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 30°F(-1°C) | 14°F(-10°C) | 1.7 in(42 mm) | 100% | 1.5 |
| FebFebruary | 34°F(1°C) | 18°F(-8°C) | 1.4 in(35 mm) | 84% | 2.5 |
| MarMarch | 47°F(8°C) | 28°F(-2°C) | 2.2 in(57 mm) | 66% | 3.6 |
| AprApril | 60°F(16°C) | 38°F(3°C) | 4.1 in(104 mm) | 60% | 4.5 |
| MayMay | 72°F(22°C) | 49°F(9°C) | 4.7 in(120 mm) | 67% | 5.1 |
| JunJune | 81°F(27°C) | 59°F(15°C) | 4.8 in(122 mm) | 68% | 5.8 |
| JulJuly | 84°F(29°C) | 62°F(17°C) | 4.1 in(104 mm) | 72% | 5.9 |
| AugAugust | 82°F(28°C) | 60°F(16°C) | 3.8 in(97 mm) | 73% | 5.2 |
| SepSeptemberBest | 76°F(25°C) | 53°F(11°C) | 3.7 in(94 mm) | 68% | 4.4 |
| OctOctober | 64°F(18°C) | 41°F(5°C) | 2.8 in(72 mm) | 68% | 2.8 |
| NovNovember | 47°F(9°C) | 30°F(-1°C) | 2.5 in(63 mm) | 76% | 1.7 |
| DecDecember | 35°F(2°C) | 19°F(-7°C) | 2.0 in(51 mm) | 80% | 1.3 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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