Chicago Weather in August

Chicago's summer weather grows stormier in August. Yet between storms August has more clear days than most months.

This page gives detailed information on the typical August temperature, precipitation, sun, humidity, wind and storms for Chicago, Illinois. The numbers here are historical averages based on temperature, rain and snow measurements gathered at Chicago Midway Airport and other climate data from Chicago O'Hare International Airport.

Temperature Weather iconTemperature

83 °F August average high 28 °C
67 °F August average low 19 °C
22 days 80 °F max. or more (27 °C)
24 days 70 °F min. or less (21 °C)

Nearly every day in August warms to over 70 degrees Fahrenheit (21 degrees Celsius) in Chicago. The city averages 5 days this month when the thermometer reaches into the 90s °F (over 32 °C). Temperatures above 100 °F (38 °C) make rare appearances here during August.

The thermometer dips to 60 °F (16 °C) or below on 4 nights. But it's not normal for August to get as cold as 50 °F (10 °C).

Rainy Weather iconRain

4.1 in total precipitation 104 mm
9 days of rain

Half the time, Chicago receives 2.3 to 5.8 inches (59 to 146 mm) of rainfall in August. One in four years has drier weather, while another one in four is wetter.

Sunny Weather iconSun

62 % sunshine
9 days clear skies

The sun's rays reach the ground in Chicago during 62 percent of daylight hours on average in August, for a total of 265 hours in the month. Typically on 9 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in August at Chicago lasts for 13 hours and 48 minutes a day on average. The longest day of the month is the 1st with 14 hours and 24 minutes of daylight. By the end of the month, the days have shortened to 13:10 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

71 % August average humidity

The relative humidity in Chicago during August usually peaks at 85 percent in the morning then drops to 55 percent by mid afternoon.

Local Time12 am3 am6 am9 am12 pm3 pm6 pm9 pm
Humidity % 81 85 85 67 57 55 61 75

Windy Weather iconWind

8.2 mph August wind speed average 13.2 kph

The wind is calmest in Chicago during August.

Stormy Weather iconStorms

3 days rainfall of 0.5 inches (13 mm) or more
6 days with thunderstorms in August

More heavy rainstorms drench Chicago in August compared with other months. The city averages two days this month when a downpour drops at least an inch (25 mm) of rain.


The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.

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