Joliet, Illinois Weather
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Climate of Joliet: monthly averages
Based on 25 years of satellite and reanalysis data (2001-2025), July is usually the hottest month in Joliet, with average daytime highs around 29°C. January is the coolest, when nights typically fall to about -9°C and frost is possible on the coldest nights. That is a wide yearly range of roughly 38°C, so the seasons feel very different from each other.
The area receives about 980 mm of rain in a typical year. Most of it falls from May to August, and May is the wettest month at roughly 117 mm.
For outdoor plans and travel, September usually offers the most comfortable weather in Joliet, with mild days and relatively little rain.
| Month | Avg high | Avg low | Rainfall | Humidity |
|---|---|---|---|---|
| Jan | 0° | -9° | 48 mm | 85% |
| Feb | 2° | -8° | 51 mm | 83% |
| Mar | 9° | -2° | 64 mm | 79% |
| Apr | 16° | 3° | 95 mm | 75% |
| May | 22° | 10° | 117 mm | 76% |
| Jun | 27° | 16° | 113 mm | 77% |
| Jul | 29° | 18° | 100 mm | 75% |
| Aug | 28° | 17° | 105 mm | 74% |
| Sep | 25° | 13° | 85 mm | 74% |
| Oct | 17° | 6° | 89 mm | 75% |
| Nov | 9° | -1° | 60 mm | 79% |
| Dec | 2° | -6° | 57 mm | 86% |
Source: NASA POWER (MERRA-2 reanalysis), averaged over the roughly 50 km grid area around Joliet. Values describe typical conditions, not a forecast.
About Joliet weather
Joliet lies in Illinois's humid continental climate, shaped by its Great Lakes and prairie geography — about 54 km south-west of Chicago. Expect warm, humid summers (June–August). Winter brings cold winters (December–February) with regular snow, colder near Lake Michigan. This page shows live, auto-refreshing weather for Joliet: current conditions, an hourly breakdown, a 16-day outlook, a date-lookup tool for any past or future date, and real-time air quality, sourced from Open-Meteo. Local timezone: America/Chicago.
Frequently asked questions
Joliet is about 54 km south-west of Chicago, in Illinois.
Joliet sees cold winters (December–February) with regular snow, colder near Lake Michigan.
The live current conditions, hourly forecast and 16-day outlook above are pulled in real time for Joliet's exact coordinates. No fixed schedule, the page updates whenever you load it.
July is usually the hottest month in Joliet, with average daytime highs of about 29°C and nights around 18°C.
The coldest nights come in January, when the average low is about -9°C and daytime highs reach around 0°C. Frost is possible on clear, calm nights.
Joliet receives about 980 mm of rain in a typical year. May is the wettest month at roughly 117 mm, and the main rainy period is May to August.
September usually offers the most comfortable weather in Joliet, with mild daytime temperatures and little rain.
In November Joliet typically sees daytime highs near 9°C and lows near -1°C, with about 60 mm of rain over the month and average humidity around 79%. Check the live forecast above for this week's actual conditions.
Up to 16 days ahead using the extended forecast and date picker above; further-out or historical dates use the same date lookup tool.
The current temperature for Joliet updates automatically at the top of this page — scroll to the hourly strip below to see how it's expected to change over the day.
Joliet's day-to-day weather follows the broader pattern of Illinois described above. See the hourly weather forecast or the air quality index for more detail.