Climate averages 1991–2020
Chicago weather
in August.
A warm, wet month: the 2nd warmest and the 9th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a warm month in Chicago: daytime highs average 26.4°C and nights cool to about 19.7°C. By daytime temperature it is the 2nd warmest of the 12 months.
Expect about 95 mm of rain on roughly 11 days, which makes August a wet month (the 9th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 52 min on an average August day.
The nearest other city in this atlas is Cicero (9 km away). In August its highs average 26.8°C, about as warm as Chicago, with 95 mm of rain.
Among the 498 cities listed in the United States, Chicago ranks joint 419th of 498 for the warmest August highs and joint 358th of 498 for the driest August (rainfall, lowest first). The mean August high of those 498 cities is 29.9°C; Chicago is 3.5°C cooler than that mean.
From August to September, average highs fall by 3.7°C to 22.7°C, and monthly rainfall falls from 95 mm to 75 mm.
The annual picture
August in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Chicago climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -0.7°C-7.4°C | -7.4°C | 62 | 9.1 | 9.510 h |
| February | 0.9°C-6.5°C | -6.5°C | 54 | 7.6 | 10.611 h |
| March | 6.0°C-1.6°C | -1.6°C | 71 | 10.3 | 11.912 h |
| April | 12.3°C4.4°C | 4.4°C | 114 | 12.4 | 13.313 h |
| May | 18.7°C10.9°C | 10.9°C | 110 | 12.4 | 14.515 h |
| June | 24.6°C17.2°C | 17.2°C | 102 | 12.1 | 15.215 h |
| July | 27.3°C20.2°C | 20.2°C | 92 | 11.5 | 14.915 h |
| August, selected | 26.4°C19.7°C | 19.7°C | 95 | 10.9 | 13.914 h |
| September | 22.7°C15.8°C | 15.8°C | 75 | 8.8 | 12.513 h |
| October | 15.9°C9.2°C | 9.2°C | 85 | 9.5 | 11.111 h |
| November | 8.4°C2.4°C | 2.4°C | 72 | 9.0 | 9.910 h |
| December | 2.2°C-3.5°C | -3.5°C | 61 | 8.7 | 9.29 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
August in nearby cities
- Cicero in AugustUnited States · 9 kmHigh 26.8°C · Low 19.1°C · 95 mm rain
- Evanston in AugustUnited States · 22 kmHigh 25.8°C · Low 20.3°C · 92 mm rain
- Hammond in AugustUnited States · 32 kmHigh 26.5°C · Low 19.6°C · 94 mm rain
- Arlington Heights in AugustUnited States · 38 kmHigh 26.4°C · Low 19.0°C · 93 mm rain
- Gary in AugustUnited States · 38 kmHigh 26.3°C · Low 19.7°C · 96 mm rain
- Bolingbrook in AugustUnited States · 39 kmHigh 26.8°C · Low 18.2°C · 95 mm rain
- Schaumburg in AugustUnited States · 41 kmHigh 26.7°C · Low 18.2°C · 93 mm rain
- Naperville in AugustUnited States · 42 kmHigh 26.8°C · Low 18.2°C · 92 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Chicago) is explained once on the Chicago year overview and on the Sources, method and limits page.
Cicero lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.