September weather forecast
Downers Grove, IL

Weather in September

The first month of the autumn, September, is still a warm month in Downers Grove, Illinois, with an average temperature fluctuating between 74.3°F (23.5°C) and 57.9°F (14.4°C).

Temperature

In September, the average high-temperature slightly decreases from 81.1°F (27.3°C) in August to a still warm 74.3°F (23.5°C). In September, in Downers Grove, the average low-temperature is 57.9°F (14.4°C).

Humidity

In September, the average relative humidity is 75%.

Rainfall

In Downers Grove, it is raining for 11.5 days, with typically 1.18" (30mm) of accumulated precipitation. Throughout the year, there are 118.5 rainfall days, and 13.74" (349mm) of precipitation is accumulated.

Snowfall

In Downers Grove, snow does not fall in May through September.

Daylight

The average length of the day in September is 12h and 28min.
On the first day of the month, sunrise is at 6:18 am and sunset at 7:25 pm. On the last day of September, sunrise is at 6:48 am and sunset at 6:35 pm CDT.

Sunshine

In Downers Grove, Illinois, the average sunshine in September is 8.7h.

UV index

The average daily maximum UV index in September in Downers Grove is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for the ordinary person.
Note: In September, the average maximum UV index of 4 translate into the following recommendations:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
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FAQ

What is the average humidity in September in Downers Grove?

In Downers Grove, the average relative humidity in September is 75%.

How many days does it rain in September in Downers Grove?

In Downers Grove, Illinois, in September, it is raining for 11.5 days, with typically 1.18" (30mm) of accumulated precipitation.

When it does not snow in Downers Grove?

May through September are months without snowfall.

Does it snow in Downers Grove in September?

In Downers Grove, Illinois, in September, it doesn't snow. In October, it regularly snows.

What is the average length of the day in September in Downers Grove?

In September, the average day length in Downers Grove is 12h and 28min.

When is the sunrise / sunset in September in Downers Grove?

On the first day of September in Downers Grove, Illinois, sunrise is at 6:18 am and sunset at 7:25 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 Downers Grove?

In Downers Grove, Illinois, the average sunshine duration in September is 8.7h.

What is the UV index reading in September in Downers Grove?

The average daily maximum UV index in September in Downers Grove, Illinois, is 4. A UV Index of 3 to 5 symbolizes a moderate health threat from unsafe exposure to Sun's UV rays.

Average temperature in September
Downers Grove, IL

Average temperature in September - Downers Grove, IL
  • Average high temperature in September: 23.5°C

The warmest month (with the highest average high temperature) is July (28°C).
The month with the lowest average high temperature is January (-1.8°C).

  • Average low temperature in September: 14.4°C

The month with the highest average low temperature is July (19.1°C).
The coldest month (with the lowest average low temperature) is January (-8.3°C).

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Average pressure in September
Downers Grove, IL

Average pressure in September - Downers Grove, IL
  • Average pressure in September: 1017mbar

The month with the highest atmospheric pressure is January (1019.7mbar).
The month with the lowest atmospheric pressure is June (1013.3mbar).

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Average wind speed in September
Downers Grove, IL

Average wind speed in September - Downers Grove, IL
  • Average wind speed in September: 11.3km/h

The windiest month (with the highest average wind speed) is January (15.6km/h).
The calmest month (with the lowest average wind speed) is August (9.8km/h).

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Average humidity in September
Downers Grove, IL

Average humidity in September - Downers Grove, IL
  • Average humidity in September: 75%

The months with the highest relative humidity are January and February (82%).
The month with the lowest relative humidity is October (72%).

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Average rainfall in September
Downers Grove, IL

Average rainfall in September - Downers Grove, IL
  • Average rainfall in September: 30mm

The wettest month (with the highest rainfall) is May (50mm).
The driest month (with the least rainfall) is December (16mm).

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Average rainfall days in September
Downers Grove, IL

Average rainfall days in September - Downers Grove, IL
  • Average rainfall days in September: 11.5 days

The month with the highest number of rainy days is May (14.9 days).
The month with the least rainy days is February (4.2 days).

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Average snowfall in September
Downers Grove, IL

Average snowfall in September - Downers Grove, IL
  • Average snowfall in September: 0mm

The month with the highest snowfall is February (58mm).
The months with the least snowfall are May, June, July, August and September (0mm).

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Average snowfall days in September
Downers Grove, IL

Average snowfall days in September - Downers Grove, IL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (9.7 days).
The 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
Downers Grove, IL

Average daylight in September / Average sunshine in September - Downers Grove, IL
  • Average daylight in September: 12h and 28min

The month with the longest days is June (Average daylight: 15h and 10min).
The month with the shortest days is December (Average daylight: 9h and 12min).

  • Average sunshine in September: 8.7h

The month with the most sunshine is August (Average sunshine: 10h).
The month with the least sunshine is January (Average sunshine: 3.7h).

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Average sunshine days in September
Downers Grove, IL

Average sunshine days in September - Downers Grove, IL
  • Average sunshine days in September: 16.1 days

The month with the most sunshine days is December (20.7 days).
The month with the least sunshine days is July (11.8 days).

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Average UV index in September
Downers Grove, IL

Average UV index in September - Downers Grove, IL
  • Average UV index in September: 4

The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).

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Average cloud cover in September
Downers Grove, IL

Average cloud cover in September - Downers Grove, IL
  • Average cloud cover in September: 32

The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 31).

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Average visibility in September
Downers Grove, IL

Average visibility in September - Downers Grove, IL
  • Average visibility in September: 9km

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (9km).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (9km).

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