Oswego, Illinois Climate by Month
Oswego, Illinois, United States
Warm summers and freezing winters, with rain spread through the year.
Oswego has warm summers and freezing winters, with rain spread through the year. July is the warmest month, with highs around 85°F (29°C); January is the coolest at 32°F (0°C), and nights dip to 15°F (-9°C). It gets 39 in (990 mm) of rain a year, spread across the months.
- Warmest month
- 85°F(29°C)
- Average high, July
- Coldest nights
- 15°F(-9°C)
- Average low, January
- Rain per year
- 39 in(990 mm)
- No clear rainy season
- Humidity
- 73%
- Sunniest: July
Best and worst months in Oswego
Best for weatherSeptember is the best time for weather in Oswego: highs near 77°F (25°C) and about 3.5 in (90 mm) of rain a month.
Least pleasantJanuary is the least pleasant month: it's the coldest, with highs of only 32°F (0°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)
Oswego weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 32°F(0°C) | 15°F(-9°C) | 1.7 in(44 mm) | 94% | 1.4 |
| FebFebruary | 36°F(2°C) | 19°F(-7°C) | 1.6 in(41 mm) | 79% | 2.5 |
| MarMarch | 48°F(9°C) | 29°F(-2°C) | 2.3 in(59 mm) | 75% | 3.6 |
| AprApril | 61°F(16°C) | 38°F(4°C) | 4.4 in(113 mm) | 66% | 4.5 |
| MayMay | 73°F(23°C) | 49°F(9°C) | 4.8 in(121 mm) | 66% | 5.2 |
| JunJune | 82°F(28°C) | 59°F(15°C) | 4.9 in(124 mm) | 67% | 5.8 |
| JulJuly | 85°F(29°C) | 63°F(17°C) | 4.0 in(101 mm) | 70% | 5.9 |
| AugAugust | 83°F(28°C) | 61°F(16°C) | 4.0 in(102 mm) | 75% | 5.1 |
| SepSeptemberBest | 77°F(25°C) | 53°F(12°C) | 3.5 in(90 mm) | 71% | 4.4 |
| OctOctober | 64°F(18°C) | 42°F(5°C) | 3.0 in(75 mm) | 66% | 2.8 |
| NovNovember | 49°F(9°C) | 31°F(-1°C) | 2.6 in(66 mm) | 72% | 1.7 |
| DecDecember | 36°F(2°C) | 20°F(-6°C) | 2.1 in(54 mm) | 76% | 1.3 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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