Crystal Lake (IL) Weather & Climate: Best Time to Visit

In Crystal Lake, temperatures differ significantly between summer and winter months. On average, daytime temperatures range from a comfortable 28°C (82°F) in July to a very cold -1°C (30°F) in January.

Nighttime temperatures range from 16°C (61°F) in July to -11°C (12°F) in January.

Check out our detailed temperature page for more information.

Temperature ranges by month

Crystal Lake experiences significant rain/snowfall throughout the year, averaging 1004 mm (40 in) of precipitation annually. The seasons in Crystal Lake bring significant changes in precipitation. The wettest month, June, receives high rainfall, with an average of 131 mm (5.2 in) of precipitation. This rainfall is distributed across 14 rainy days.

In contrast, the driest month, January, experiences much less snowfall, totaling 41 mm (1.6 in) over 9 snowy days. These distinct seasonal differences provide diverse experiences throughout the year. For more details, please visit our Crystal Lake Precipitation page.

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

The average number of days each month with precipitation

In Crystal Lake, summer days are longer and more sunny, with daily sunshine hours peaking at 10.6 hours in July. As the darker season arrives, the brightness of the sun becomes less. December sees a soft sun for only 3.6 hours per average 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 Crystal Lake.

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