Joliet, IL weather in September
In September, Joliet sees highs around 76°F and lows around 55°F: mild, with some rain. There are about 8 days with rain. Good for outdoor plans.
- Normal high
- 76°F
- Normal low
- 55°F
- Wet days
- 8
- 3.2 in total
- Muggy days
- 3
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 80°F | 71°F |
| Normal low | 61°F | 49°F |
| Chance of a wet day | 27% | 28% |
| Sunrise / sunset | 6:18 am / 7:26 pm | 6:48 am / 6:36 pm |
| Daylight | 13.1 h | 11.8 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 September day
- 6 am61°Fdew point 54°F
- 9 am68°Fdew point 55°F
- Noon73°Fdew point 54°F
- 3 pm74°Fdew point 54°F
- 6 pm70°Fdew point 54°F
- 9 pm67°Fdew point 55°F
NOAA hourly normals (local standard time) from Chicago Midway Airport (25 mi away); average wind 9 mph.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F14 of 30
- Hot dayshigh 90°F or more2 of 30
- Muggy daysdaily mean dew point 65°F or more3 of 30
- Wet daysat least 0.01 in of rain or melted snow8 of 30
- Notable rainat least 0.10 in5 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 3.2 in; a dry September brings about 1.8 in and a wet one about 3.6 in (25th and 75th percentiles). About 2 days bring half an inch or more, and about 1 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202002: average high 82°F
- Coolest September1993: average high 68°F
- Wettest September2008: 11.6 in
- Driest September2017: 0.2 in
- Highest reading95°F (September 10, 2002)
- Lowest reading33°F (September 24, 1995)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 82°F | 76°F | 63°F |
| Normal low | 63°F | 55°F | 43°F |
| Wet days | 9 | 8 | 10 |
| Comfortable days | 7 | 14 | 12 |
| Daylight | 13.8 h | 12.5 h | 11.1 h |
Highs change by -6°F from August and -13°F into October.
Nearby alternatives in September
- Warmer: Evansville, IN247 mi · high 82°F · 8 wet days
How Joliet ranks in September
- Normal high253rd warmest of 378 cities; 4th of 8 in Illinois
- Wet days196th driest of 378
- Comfortable days99th most of 342
What to pack for Joliet in September
- A rain jacket or umbrella – rain on about 8 days
Heating and cooling
September has 83 heating degree days and 105 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Joliet in September?
The normal high is 76°F and the normal low is 55°F. From 1991 to 2020 the hottest September reading was 95°F (most recently on September 10, 2002).
Does it rain a lot in Joliet in September?
About 8 days in September have at least 0.01 in of precipitation, and the normal total is 3.2 in. The wettest September in 1991-2020 was in 2008 (11.6 in); the driest was in 2017 (0.2 in).
Is September a good time to visit Joliet?
September ranks 2nd of 12 months on our comfort score for Joliet (67 out of 100). It has about 14 comfortable days and about 2 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).