August is one of the warmer months of the year in Joliet, with average highs near 28.2°C and lows around 16.9°C (mean 22.5°C). It is a relatively wet time of year, averaging 100 mm of rainfall and 73% relative humidity across the period.
August is one of the warmer months of the year in Joliet. Across 45 years of records, the warmest August in Joliet was 1988 — when the month averaged 25.8°C — while the coldest was 1992 at 19.4°C. Typical August days reach 28.2°C with nights near 16.9°C. The long-term trend is warming, about 0.2°C per decade.
August is a relatively wet time of year in Joliet, averaging 100 mm of rainfall. The wettest August on record was 2007 with 265 mm, while the driest was 2020 at 33 mm.
Relative humidity in Joliet during August averages 73%. The most humid August was 1993 at 85%, and the least humid was 1988 at 57%.
August receives about 5.4 kWh/m²/day of solar energy in Joliet. The sunniest Augusts were 2011 and 2020 at 6 kWh/m²/day, and the cloudiest was 1993 at 4.7.
Average wind speed in Joliet during August is 2.2 m/s. The windiest Augusts were 1988 and 2009 at 2.6 m/s, while the calmest was 1995 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 22.3°C | 21.9°C | 22.8°C | 22.6°C | 23.4°C | +1.1°C |
| Avg High | 28.2°C | 27.4°C | 28.6°C | 27.9°C | 29.2°C | +1°C |
| Avg Low | 16.4°C | 16.5°C | 17.1°C | 17.3°C | 17.5°C | +1.1°C |
| Avg Rain | 103 mm | 95 mm | 115 mm | 98 mm | 79 mm | -25 mm |
August temperatures in Joliet have risen by about 1.4°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 5.9°C (1986) to a record high of 39.6°C (1988).
Rainfall in August is a relatively wet time of year, averaging 100 mm, with a wettest year of 265 mm.
One of the best times to visit Joliet
August is one of the best times to visit Joliet. Expect days averaging 28.2°C and nights around 16.9°C (mean 22.5°C) — warmer than Joliet's yearly average — with higher rainfall (100 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 28.3°C | 22.7°C | 17.0°C | 34.6°C | 9.8°C | 105 mm | 71% | 2.1 m/s | 5.9 |
| 2024 | 29.4°C | 23.4°C | 17.3°C | 35.4°C | 11.6°C | 80 mm | 68% | 2.2 m/s | 5.6 |
| 2023 | 29.7°C | 23.3°C | 16.9°C | 38.7°C | 11.6°C | 65 mm | 69% | 2.4 m/s | 5.5 |
| 2022 | 29.1°C | 23.3°C | 17.4°C | 34.5°C | 13.4°C | 99 mm | 71% | 2.3 m/s | 5.2 |
| 2021 | 30.3°C | 24.8°C | 19.3°C | 33.5°C | 13.1°C | 91 mm | 72% | 2.1 m/s | 5.6 |
| 2020 | 28.6°C | 22.8°C | 17.0°C | 34.0°C | 11.6°C | 33 mm | 72% | 1.9 m/s | 6 |
| 2019 | 26.7°C | 21.7°C | 16.8°C | 29.6°C | 12.5°C | 74 mm | 79% | 2 m/s | 5.6 |
| 2018 | 29.6°C | 24.0°C | 18.4°C | 34.2°C | 13.0°C | 102 mm | 74% | 2.2 m/s | 5.1 |
| 2017 | 26.1°C | 20.6°C | 15.2°C | 30.8°C | 10.8°C | 58 mm | 74% | 2.1 m/s | 5.5 |
| 2016 | 27.7°C | 23.4°C | 19.1°C | 32.5°C | 13.9°C | 177 mm | 81% | 2 m/s | 5.3 |
| 2015 | 26.4°C | 21.2°C | 16.1°C | 30.3°C | 11.0°C | 80 mm | 78% | 2.2 m/s | 5.5 |
| 2014 | 27.5°C | 22.5°C | 17.6°C | 30.2°C | 10.2°C | 143 mm | 79% | 2 m/s | 4.9 |
| 2013 | 28.1°C | 22.5°C | 16.8°C | 33.9°C | 11.7°C | 74 mm | 73% | 2.1 m/s | 5.6 |
| 2012 | 30.7°C | 23.6°C | 16.5°C | 37.0°C | 11.2°C | 93 mm | 59% | 2 m/s | 5.7 |
| 2011 | 27.7°C | 22.5°C | 17.4°C | 32.0°C | 12.8°C | 102 mm | 77% | 2 m/s | 6 |
| 2010 | 28.5°C | 23.6°C | 18.7°C | 32.1°C | 13.3°C | 74 mm | 80% | 2 m/s | 5.8 |
| 2009 | 25.3°C | 20.5°C | 15.6°C | 31.0°C | 7.9°C | 133 mm | 82% | 2.6 m/s | 5 |
| 2008 | 27.6°C | 21.8°C | 16.0°C | 31.6°C | 12.5°C | 56 mm | 74% | 2.1 m/s | 5.8 |
| 2007 🌧️ | 28.6°C | 23.8°C | 19.1°C | 32.5°C | 12.6°C | 265 mm | 80% | 2.1 m/s | 5.1 |
| 2006 | 28.8°C | 23.3°C | 17.8°C | 36.8°C | 12.6°C | 115 mm | 71% | 2.4 m/s | 4.8 |
| 2005 | 30.5°C | 24.4°C | 18.3°C | 35.8°C | 13.6°C | 75 mm | 65% | 2.1 m/s | 5.4 |
| 2004 | 26.1°C | 20.4°C | 14.7°C | 32.9°C | 9.1°C | 159 mm | 72% | 2.4 m/s | 5 |
| 2003 | 29.8°C | 23.7°C | 17.7°C | 38.1°C | 15.2°C | 66 mm | 70% | 2.3 m/s | 5.5 |
| 2002 | 29.6°C | 23.4°C | 17.3°C | 34.2°C | 12.4°C | 105 mm | 71% | 2.4 m/s | 5.5 |
| 2001 | 30.1°C | 23.7°C | 17.4°C | 36.9°C | 13.0°C | 119 mm | 68% | 2.3 m/s | 5.4 |
| 2000 | 29.4°C | 23.0°C | 16.7°C | 35.6°C | 11.1°C | 58 mm | 71% | 2.5 m/s | 5.6 |
| 1999 | 28.3°C | 22.1°C | 16.0°C | 33.5°C | 11.4°C | 69 mm | 67% | 2.3 m/s | 5.1 |
| 1998 | 28.3°C | 23.1°C | 17.9°C | 33.0°C | 13.6°C | 96 mm | 77% | 2 m/s | 5.2 |
| 1997 | 27.2°C | 21.4°C | 15.5°C | 34.7°C | 11.1°C | 125 mm | 74% | 2.4 m/s | 4.9 |
| 1996 | 26.9°C | 21.5°C | 16.1°C | 31.2°C | 12.8°C | 46 mm | 79% | 1.9 m/s | 5.6 |
| 1995 | 29.3°C | 24.7°C | 20.0°C | 32.8°C | 14.2°C | 108 mm | 82% | 1.8 m/s | 5.2 |
| 1994 | 25.6°C | 20.0°C | 14.4°C | 31.6°C | 9.0°C | 114 mm | 78% | 2.4 m/s | 4.8 |
| 1993 | 26.6°C | 22.2°C | 17.9°C | 31.2°C | 11.7°C | 132 mm | 85% | 2.2 m/s | 4.7 |
| 1992 ❄️ | 25.5°C | 19.4°C | 13.4°C | 30.7°C | 9.8°C | 61 mm | 73% | 2.4 m/s | 5.3 |
| 1991 | 29.8°C | 23.5°C | 17.3°C | 36.4°C | 14.0°C | 66 mm | 65% | 2.2 m/s | 5.4 |
| 1990 | 26.3°C | 21.3°C | 16.3°C | 30.8°C | 11.2°C | 138 mm | 81% | 2.1 m/s | 5.4 |
| 1989 | 27.5°C | 21.8°C | 16.1°C | 32.0°C | 10.0°C | 136 mm | 73% | 2.2 m/s | 5.3 |
| 1988 🔥 | 32.5°C | 25.8°C | 19.0°C | 39.6°C | 9.5°C | 87 mm | 57% | 2.6 m/s | 5.4 |
| 1987 | 27.4°C | 22.1°C | 16.8°C | 36.6°C | 9.1°C | 224 mm | 75% | 2.4 m/s | 4.8 |
| 1986 | 26.4°C | 20.2°C | 13.9°C | 31.0°C | 5.9°C | 53 mm | 67% | 2.2 m/s | 5.3 |
| 1985 | 27.3°C | 21.2°C | 15.2°C | 31.7°C | 11.0°C | 87 mm | 71% | 2.2 m/s | 5.1 |
| 1984 | 30.1°C | 23.4°C | 16.8°C | 37.1°C | 10.5°C | 48 mm | 66% | 2.2 m/s | 5.5 |
| 1983 | 30.3°C | 24.3°C | 18.2°C | 36.4°C | 12.1°C | 87 mm | 71% | 2.1 m/s | — |
| 1982 | 26.2°C | 20.6°C | 15.0°C | 31.4°C | 8.9°C | 61 mm | 75% | 2.1 m/s | — |
| 1981 | 26.1°C | 21.2°C | 16.4°C | 28.9°C | 11.0°C | 149 mm | 81% | 2.2 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 28.2°C with lows near 16.9°C (mean 22.5°C), based on 45 years of NASA POWER data.
August averages 100 mm of rainfall in Joliet, a relatively wet time of year. The wettest on record was 265 mm in 2007.
The hottest August reached 39.6°C in 1988. The coldest dipped to 5.9°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 1.4°C. Daytime highs moved from 28°C to 29.4°C and overnight lows from 16.3°C to 17.6°C over the same span.
August is one of the warmer months of the year in Joliet and a relatively wet time of year, so plan for around 28.2°C daytime highs and 16.9°C at night.
Not quite — August is the 11th coolest month in Joliet, averaging 22.5°C.
For August in Joliet, pack light layers you can adjust through the day, with typical highs of 28.2°C and lows of 16.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 73% — moderately humid.
Average wind speed in August is 2.2 m/s. The windiest August on record averaged 2.6 m/s (1988).
The wettest August on record was 2007 with 265 mm. On average, August sees 100 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Joliet behaves each August, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for August specifically, along with year-by-year records and how the month has changed over the decades.
