September weather forecast and climate
Naperville, IL

A covered bridge over a river along the famous Naperville Riverwalk in Naperville, Illinois
A covered bridge over a river along the famous Naperville Riverwalk in Naperville, Illinois

Weather in September

September, the first month of the autumn, in Naperville, is also a moderately hot month, with average temperature varying between 57°F (13.9°C) and 73.8°F (23.2°C).

Temperature

In September, the average high-temperature marginally drops, from a warm 80.1°F (26.7°C) in August, to a still moderately hot 73.8°F (23.2°C). In Naperville, in September, the average low-temperature is 57°F (13.9°C).

Humidity

In September, the average relative humidity in Naperville, Illinois, is 77%.

Rainfall

In Naperville, in September, it is raining for 12.2 days, with typically 1.38" (35mm) of accumulated precipitation. Throughout the year, there are 132.2 rainfall days, and 16.22" (412mm) of precipitation is accumulated.

Snowfall

May through September are months without snowfall.

Daylight

In September, the average length of the day is 12.5h.

Sunshine

In Naperville, the average sunshine is 8.8h.

UV index

The average daily maximum UV index in Naperville is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from the exposure to the Sun's UV rays for average individuals.
Note: The daily maximum UV index of 4 interpret into the following advice:
Take precautions - Protection against sun damage is advised. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the average humidity in September in Naperville?

In September, the average relative humidity in Naperville is 77%.

How much does it rain in Naperville in September?

In Naperville, Illinois, in September, it is raining for 12.2 days, with typically 1.38" (35mm) of accumulated precipitation.

When it does not snow in Naperville?

In Naperville snow does not fall in May through September.

Does it snow in Naperville in September?

In Naperville, in September, it doesn't snow. In October, it regularly snows.

How many hours of daylight does Naperville have in September?

The average length of the day in September is 12.5h.

How long on average sun shines in September in Naperville?

The average sunshine in September in Naperville, Illinois, is 8.8h.

What is the UV index reading in September in Naperville?

In September, the average daily maximum UV index in Naperville is 4. A UV Index reading of 3 to 5 represents a moderate health threat from unsafe exposure to the Sun's UV rays.

Average temperature in September
Naperville, IL

Average temperature in September - Naperville, IL
  • Average high temperature in September: 73.8°F

The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is January (28.4°F).

  • Average low temperature in September: 57°F

The month with the highest average low temperature is July (65.1°F).
The coldest month (with the lowest average low temperature) is January (17.1°F).

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Average pressure in September
Naperville, IL

Average pressure in September - Naperville, IL
  • Average pressure in September: 30.03"

The month with the highest atmospheric pressure is January (30.11").
The month with the lowest atmospheric pressure is June (29.92").

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Average wind speed in September
Naperville, IL

Average wind speed in September - Naperville, IL
  • Average wind speed in September: 7mph

The windiest month (with the highest average wind speed) is January (9.7mph).
The calmest month (with the lowest average wind speed) is August (6mph).

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Average humidity in September
Naperville, IL

Average humidity in September - Naperville, IL
  • Average humidity in September: 77%

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

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Average rainfall in September
Naperville, IL

Average rainfall in September - Naperville, IL
  • Average rainfall in September: 1.38"

The wettest month (with the highest rainfall) is May (2.09").
The driest month (with the least rainfall) is December (0.71").

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Average rainfall days in September
Naperville, IL

Average rainfall days in September - Naperville, IL
  • Average rainfall days in September: 12.2 days

The month with the highest number of rainy days is July (17.3 days).
The month with the least rainy days is February (4.4 days).

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Average snowfall in September
Naperville, IL

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

The month with the highest snowfall is January (1.85").
Months with the least snowfall are May, June, July, August and September (0").

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Average snowfall days in September
Naperville, IL

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

The month with the highest number of snowfall days is January (11.1 days).
Months with the least snowfall days are June, July, August and September (0 days).

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

Average daylight in September / Average sunshine in September - Naperville, IL
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.2h).
The month with the shortest days is December (Average daylight: 9.2h).

  • Average sunshine in September: 8.8h

Months with the most sunshine are July and August (Average sunshine: 10h).
The month with the least sunshine is January (Average sunshine: 3.8h).

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Average sunshine days in September
Naperville, IL

Average sunshine days in September - Naperville, IL
  • Average sunshine days in September: 14.5 days

The month with the most sunshine days is November (19.6 days).
The month with the least sunshine days is July (10.2 days).

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Average UV index in September
Naperville, IL

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

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January and December (UV index 1).

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Average cloud cover in September
Naperville, IL

Average cloud cover in September - Naperville, IL
  • Average cloud cover in September: 31

The month with the most cloud cover is January (Cloud cover 60).
Months with the least cloud cover are August and September (Cloud cover 31).

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Average visibility in September
Naperville, IL

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

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

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