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

The climate in Harvey is known for significant temperature differences throughout the year, making the weather dynamic. Average maximum daytime temperatures range from a comfortable 29°C (84°F) in July, the warmest time of the year, to a very cold 0°C (32°F) during cooler months like January.

At night, you can expect temperatures ranging from 19°C (66°F) in July to around -8°C (18°F) during January.

Check out our detailed temperature page for more information.

Temperature ranges by month

Harvey has a notably wet climate with abundant precipitation, recording 1060 mm (42 in) of rain/snowfall per year. Significant seasonal changes in precipitation occur throughout the year. In the wettest month, August it receives high rainfall, averaging 122 mm (4.8 in) of precipitation, recorded across 11 rainy days. In contrast, the driest month November brings less rainfall, with 54 mm (2.1 in) over 8 rainy days. For more details, please visit our Harvey Precipitation page.

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

The average number of days each month with precipitation

Seasonal changes in sunshine hours are quite dramatic in Harvey. While July receives considerable daily sunshine with up to 10.6 hours, December marks the darkest time of the year, where sunshine is scarce 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 Harvey.

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