September weather forecast
Joliet, IL

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A unique shot of cars, trees, and buildings along a street in the town of Joliet, Illinois
A unique shot of cars, trees, and buildings along a street in the town of Joliet, Illinois

Weather in September

September is an epitome of a transitional month in Joliet, with summer slowly yielding to the upcoming fall. The temperature drops moderately from August’s 80.1°F (26.7°C) to a comfortable 74.7°F (23.7°C). As autumn nears, daylight hours decrease while mild winds begin to sway, signalling a change in season. Humidity lessens, and condensation levels dip facilitating strikingly clear visibility.

Temperature

With the arrival of September, Joliet notices a mild change in the average high-temperature, sliding from August's moderately hot 80.1°F (26.7°C) to a still warm 74.7°F (23.7°C). An average low-temperature of 56.7°F (13.7°C) is noted during the nights in September.

Humidity

In Joliet, the average relative humidity in September is 78%.

Rainfall

In September, in Joliet, the rain falls for 12.5 days. Throughout September, 2.48" (63mm) of precipitation is accumulated. Throughout the year, there are 153.6 rainfall days, and 32.72" (831mm) of precipitation is accumulated.

Snowfall

In Joliet, Illinois, snow does not fall in May through October.

Daylight

The average length of the day in September is 12h and 28min.
On the first day of the month, sunrise is at 6:19 am and sunset at 7:24 pm. On the last day of September, in Joliet, sunrise is at 6:48 am and sunset at 6:35 pm CDT.

Sunshine

In September, the average sunshine in Joliet is 8.5h.

UV index

The average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for the average person.
Note: The UV index of 4 during September translates into the following guidance:
Be mindful. Individuals with a lighter skin tone may suffer burns in less than 30 minutes. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. To mitigate harm from sun exposure, pick sunglasses offering UVA and UVB defense.
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Frequently asked questions

What is the usual temperature for Joliet in September?

In September, the average high-temperature and low-temperature in Joliet are 74.7°F (23.7°C) and 56.7°F (13.7°C) respectively. In July, the average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which factors the actual air temperature with the relative humidity, is calculated to be 87.8°F (31°C).

What is the average humidity in September in Joliet?

The average relative humidity in September in Joliet is 78%.

How much does it rain in Joliet in September?

In Joliet, in September, it is raining for 12.5 days, with typically 2.48" (63mm) of accumulated precipitation.

When it does not snow in Joliet?

May through October are months without snowfall in Joliet.

How many hours of daylight does Joliet have in September?

In Joliet, Illinois, the average day length in September is 12h and 28min.

What time are sunrise and sunset in September in Joliet?

In September, on the first day of the month, sunrise is at 6:19 am and sunset at 7:24 pm. On the last day of the month, sunrise is at 6:48 am and sunset at 6:35 pm CDT.

How long on average sun shines in September in Joliet?

The average sunshine duration in September in Joliet is 8.5h.

What is the UV index intensity in September in Joliet?

In September, the average daily maximum UV index in Joliet, Illinois, is 4. A UV Index value of 3 to 5 symbolizes a medium health risk from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Joliet, IL

Average temperature in September - Joliet, IL
  • Average high temperature in September: 74.7°F

The warmest month (with the highest average high temperature) is July (81.3°F).
The month with the lowest average high temperature is January (29.3°F).

  • Average low temperature in September: 56.7°F

The month with the highest average low temperature is July (64.8°F).
The coldest month (with the lowest average low temperature) is January (17.4°F).

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Average pressure in September
Joliet, IL

Average pressure in September - Joliet, IL
  • Average pressure in September: 30.03"Hg

The month with the highest atmospheric pressure is January (30.12"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in September
Joliet, IL

Average wind speed in September - Joliet, IL
  • Average wind speed in September: 6.9mph

The windiest month (with the highest average wind speed) is April (9.7mph).
The calmest month (with the lowest average wind speed) is August (5.9mph).

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Average humidity in September
Joliet, IL

Average humidity in September - Joliet, IL
  • Average humidity in September: 78%

The month with the highest relative humidity is February (83%).
The month with the lowest relative humidity is October (73%).

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Average rainfall in September
Joliet, IL

Average rainfall in September - Joliet, IL
  • Average rainfall in September: 2.48"

The wettest month (with the highest rainfall) is May (4.41").
The driest month (with the least rainfall) is February (1.61").

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Average rainfall days in September
Joliet, IL

Average rainfall days in September - Joliet, IL
  • Average rainfall days in September: 12.5 days

The month with the highest number of rainy days is July (17.9 days).
The month with the least rainy days is February (5.7 days).

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Average snowfall in September
Joliet, IL

Average snowfall in September - Joliet, IL
  • Average snowfall in September: 0"

The month with the highest snowfall is January (4.33").
The months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in September
Joliet, IL

Average snowfall days in September - Joliet, IL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (11.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).

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Average daylight in September /
Average sunshine in September
Joliet, IL

Average daylight in September / Average sunshine in September - Joliet, IL
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 12min).

  • Average sunshine in September: 8h and 3min

The month with the most sunshine is August (Average sunshine: 9h and 42min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).

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Average sunshine days in September
Joliet, IL

Average sunshine days in September - Joliet, IL
  • Average sunshine days in September: 15 days

The month with the most sunshine days is November (18.1 days).
The month with the least sunshine days is June (10.4 days).

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Average UV index in September
Joliet, IL

Average UV index in September - Joliet, IL
  • Average UV index in September: 4

The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January and December (UV index 1).

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Average cloud cover in September
Joliet, IL

Average cloud cover in September - Joliet, IL
  • Average cloud cover in September: 34

The month with the most cloud cover is January (Cloud cover 60).
The months with the least cloud cover are August and September (Cloud cover 34).

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Average visibility in September
Joliet, IL

Average visibility in September - Joliet, IL
  • Average visibility in September: 6mi

The months with the highest visibility are March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are January, February, July and August (5mi).

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Joliet, Illinois, USA

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