Oswego (IL) Weather & Climate: Best Time to Visit

In Oswego, temperatures differ significantly between summer and winter months. Average daytime temperatures reach a comfortable 29°C (84°F) in July. In January, the coolest month of the year, temperatures drop to a very cold -1°C (30°F).

At night, temperatures range from around 17°C (63°F) in July to -10°C (14°F) in January.

Check out our detailed temperature page for more information.

Temperature ranges by month

Oswego experiences significant rain/snowfall throughout the year, averaging 1029 mm (41 in) of precipitation annually. Oswego can be quite wet during June, receiving approximately 130 mm (5.1 in) of precipitation over 14 rainy days.

In contrast, during the driest month (January), you will experience much drier conditions, with 47 mm (1.9 in) of precipitation spread across 10 snowy days. For more details, please visit our Oswego Precipitation page.

The mean monthly precipitation over the year, including rain, hail, and snow

The average number of days each month with precipitation

Oswego can be enjoyed more throughout the sunniest month of July under a blue sky, with approximately 10.6 hours of sunshine daily. In contrast, the city experiences much darker days in December, with only 3.6 hours of sunlight per day.

Visit our detailed sunshine hours page for more information.

Monthly hours of sunshine

Daily hours of sunshine

Daily percentage of sunshine

The relative humidity is high throughout the year in Oswego.

The city experiences its highest humidity in December, reaching 76%. In May, the humidity drops to its lowest level at 64%. What does this mean? Read our detailed page on humidity levels for further details.

Relative humidity over the year