September Weather in Joliet, United States

Last updated: June 24, 2025

In September, the average temperature in Joliet, United States hovers around 15°C (60°F). Be prepared for a range, with minimums dipping to -1°C (31°F) and maximums soaring to 36°C (97°F). Expect about 57 mm (2.2 in) of precipitation spread over 6 days, accompanied by an average humidity of 76%. Stay dry and comfortable as you enjoy this variable weather!

September Temperature in Joliet

In September in Joliet, the weather can vary significantly, so it's essential to pack for both warm and chilly conditions.

September Weather in Joliet: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Joliet, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Joliet, September typically has an average temperature of 15°C (60°F), with highs reaching up to 36°C (97°F) and lows dropping to around -1°C (31°F).

Data source: Temperature data for Joliet generated using information from the Copernicus Climate Change Service.

September Precipitation in Joliet

In Joliet in September, the precipitation amount is 57 mm (2.2 in) over a span of 6 days.

September Precipitation Trends in Joliet

The chart displays monthly precipitation patterns in Joliet, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Joliet, September typically receives around 57 mm (2.2 inches) of precipitation spread over approximately 6 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Joliet

In Joliet in September humidity is 76%. With an average temperature of 15°C (60°F), this humidity feels like a warm, damp blanket wrapping around you, making outdoor activities a bit more challenging and urging you to stay hydrated while exploring the area.

September Average Humidity in Joliet

This chart illustrates the average monthly humidity levels in Joliet, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Joliet is approximately 76%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Joliet

In Joliet in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Joliet.

Maximum UV Index Levels in Joliet for September

The chart shows the monthly maximum UV Index (UVI) for Joliet in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Joliet typically reaches 8, which falls under the very high exposure category.

Data source: Joliet September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How September Weather in Joliet Compares to Other Months

Weather in Joliet varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Joliet, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Joliet, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (25°F)	21 mm (0.8 inches)	85%	moderate
February Weather	-7°C (20°F)	46 mm (1.8 inches)	85%	moderate
March Weather	2°C (35°F)	44 mm (1.7 inches)	79%	high
April Weather	5°C (42°F)	76 mm (3.0 inches)	74%	very high
May Weather	12°C (53°F)	82 mm (3.2 inches)	76%	very high
June Weather	18°C (64°F)	76 mm (3.0 inches)	79%	extreme
July Weather	22°C (72°F)	32 mm (1.3 inches)	81%	very high
August Weather	21°C (69°F)	25 mm (1.0 inches)	80%	very high
September Weather	15°C (60°F)	57 mm (2.2 inches)	76%	very high
October Weather	6°C (43°F)	57 mm (2.2 inches)	74%	moderate
November Weather	1°C (35°F)	34 mm (1.3 inches)	81%	moderate
December Weather	-3°C (28°F)	30 mm (1.2 inches)	87%	low