Joliet, IL weather in August
Joliet is warm and often humid in August, with some rain: highs average 82°F and nights drop to about 63°F. Rain falls on about 9 days. This is the peak of the warm season in Joliet.
- Normal high
- 82°F
- Normal low
- 63°F
- Wet days
- 9
- 4.0 in total
- Muggy days
- 11
- dew point 65°F+
How August changes from start to finish
| August 1 | August 31 | |
|---|---|---|
| Normal high | 83°F | 80°F |
| Normal low | 64°F | 61°F |
| Chance of a wet day | 30% | 28% |
| Sunrise / sunset | 5:47 am / 8:10 pm | 6:17 am / 7:27 pm |
| Daylight | 14.4 h | 13.2 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Central Time).
A typical August day
- 6 am68°Fdew point 62°F
- 9 am75°Fdew point 62°F
- Noon79°Fdew point 61°F
- 3 pm80°Fdew point 61°F
- 6 pm77°Fdew point 61°F
- 9 pm74°Fdew point 62°F
NOAA hourly normals (local standard time) from Chicago Midway Airport (25 mi away); average wind 8 mph.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F7 of 31
- Hot dayshigh 90°F or more3 of 31
- Muggy daysdaily mean dew point 65°F or more11 of 31
- Wet daysat least 0.01 in of rain or melted snow9 of 31
- Notable rainat least 0.10 in6 of 31
- Freezing nightslow 32°F or below0 of 31
- Snow on the groundsnow depth 1 in or more0 of 31
Average days per August, counted from daily records for each year 1991-2020.
Rain in August
Normal precipitation is 4.0 in; a dry August brings about 2.1 in and a wet one about 4.7 in (25th and 75th percentiles). About 3 days bring half an inch or more, and about 1 an inch or more.
How August varies from year to year
- Warmest August, 1991-20201995: average high 88°F
- Coolest August2004: average high 78°F
- Wettest August2007: 10.8 in
- Driest August1996: 0.5 in
- Highest reading99°F (August 2, 1991)
- Lowest reading47°F (August 26, 2017)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
August compared with July and September
| July | August | September | |
|---|---|---|---|
| Normal high | 84°F | 82°F | 76°F |
| Normal low | 64°F | 63°F | 55°F |
| Wet days | 9 | 9 | 8 |
| Comfortable days | 6 | 7 | 14 |
| Daylight | 14.8 h | 13.8 h | 12.5 h |
Highs change by -2°F from July and -6°F into September.
Nearby alternatives in August
- Warmer: St. Louis, MO229 mi · high 88°F · 8 wet days
How Joliet ranks in August
- Normal high279th warmest of 378 cities; 8th of 8 in Illinois
- Wet days199th driest of 378
- Comfortable days103rd most of 341
What to pack for Joliet in August
- A rain jacket or umbrella – rain on about 9 days
Heating and cooling
August has 6 heating degree days and 234 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Joliet in August?
The normal high is 82°F and the normal low is 63°F. From 1991 to 2020 the hottest August reading was 99°F (August 2, 1991).
Does it rain a lot in Joliet in August?
About 9 days in August have at least 0.01 in of precipitation, and the normal total is 4.0 in. The wettest August in 1991-2020 was in 2007 (10.8 in); the driest was in 1996 (0.5 in).
Is August a good time to visit Joliet?
August ranks 6th of 12 months on our comfort score for Joliet (59 out of 100). It has about 7 comfortable days and about 3 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Joliet Brandon Rd Dam (USC00114530), 1.9 mi SW of the city center, 543 ft . NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Chicago Midway Airport (USW00014819), 25 mi NE of the city center, 612 ft (71 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Chicago Midway Intl Arpt (725340-14819), 25 mi NE of the city center, 610 ft (69 ft higher than the city). Hourly observations, 1991-2020.
- Not available for this location: cloud cover (no station close enough or similar enough in elevation).