September weather forecast and climate
Chicago, IL

The city of Chicago in Illinois on the shores of Lake Michigan, with a superb view of the sandy beach of Oak Street
The city of Chicago in Illinois on the shores of Lake Michigan, with a superb view of the sandy beach of Oak Street

Weather in September

The first month of the autumn, September, is also an agreeable month in Chicago, Illinois, with average temperature fluctuating between 61.2°F (16.2°C) and 71.1°F (21.7°C).

Temperature

In September, the average high-temperature slightly decreases, from a warm 77.5°F (25.3°C) in August, to an agreeable 71.1°F (21.7°C). In September, in Chicago, the average low-temperature is 61.2°F (16.2°C).

Humidity

In Chicago, the average relative humidity is 75%.

Rainfall

In September, the rain falls for 14.5 days. Throughout September, 3.23" (82mm) of precipitation is accumulated. Throughout the year, there are 160.2 rainfall days, and 36.97" (939mm) of precipitation is accumulated.

Snowfall

In Chicago snow does not fall in June through October.

Ocean temperature

In Chicago, the average water temperature is 68.5°F (20.3°C).
Note: Swimming in 68.5°F (20.3°C) is not enjoyable for the majority. Controlling breathing becomes progressively more difficult as surface water temperature decreases below 69.8°F (21°C).

Daylight

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

Sunshine

In September, the average sunshine is 9.1h.

UV index

In September, the average daily maximum UV index in Chicago is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from the exposure to the Sun's UV rays for ordinary individuals.
Note: In September, the average maximum UV index of 4 translate into the following recommendations:
Take precautions - Protection against sunburn is recommended. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. 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 temperature in September in Chicago?

In September, the average high-temperature is 71.1°F (21.7°C), and the average low-temperature is 61.2°F (16.2°C).

What is the average humidity in September in Chicago?

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

How much does it rain in Chicago in September?

In Chicago, during September, the rain falls for 14.5 days and regularly aggregates up to 3.23" (82mm) of precipitation.

When it does not snow in Chicago?

In Chicago, Illinois, snow does not fall in June through October.

How cold is the water in September in Chicago?

In Chicago, Illinois, the average seawater temperature in September is 68.5°F (20.3°C). For most, swimming in 68.5°F (20.3°C) is not an enjoyable activity. Furthermore, controlling your breathing becomes progressively more difficult as the water temperature decreases from 69.8°F (21°C) to 59°F (15°C).

How many hours of daylight does Chicago have in September?

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

How many hours of sunshine does Chicago have in September?

In September, the average sunshine in Chicago is 9.1h.

What is the UV index reading in September in Chicago?

In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a medium hazard to health from the exposure to the Sun's UV radiation.

Average temperature in September
Chicago, IL

Average temperature in September - Chicago, IL
  • Average high temperature in September: 21.7°C

The warmest month (with the highest average high temperature) is August (25.3°C).
The month with the lowest average high temperature is January (-1.3°C).

  • Average low temperature in September: 16.2°C

The month with the highest average low temperature is July (19.9°C).
The coldest month (with the lowest average low temperature) is January (-6.3°C).

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Average pressure in September
Chicago, IL

Average pressure in September - Chicago, IL
  • Average pressure in September: 1017mbar

The month with the highest atmospheric pressure is January (1019.5mbar).
The month with the lowest atmospheric pressure is June (1013.3mbar).

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Average wind speed in September
Chicago, IL

Average wind speed in September - Chicago, IL
  • Average wind speed in September: 15km/h

The windiest month (with the highest average wind speed) is January (20.1km/h).
The calmest month (with the lowest average wind speed) is July (12.4km/h).

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Average humidity in September
Chicago, IL

Average humidity in September - Chicago, IL
  • Average humidity in September: 75%

The month with the highest relative humidity is January (82%).
The month with the lowest relative humidity is October (73%).

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Average rainfall in September
Chicago, IL

Average rainfall in September - Chicago, IL
  • Average rainfall in September: 82mm

The wettest month (with the highest rainfall) is June (124mm).
The driest month (with the least rainfall) is December (42mm).

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Average rainfall days in September
Chicago, IL

Average rainfall days in September - Chicago, IL
  • Average rainfall days in September: 14.5 days

The month with the highest number of rainy days is July (18.5 days).
The month with the least rainy days is February (5.5 days).

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Average snowfall in September
Chicago, IL

Average snowfall in September - Chicago, IL
  • Average snowfall in September: 0mm

The month with the highest snowfall is February (90mm).
Months with the least snowfall are June, July, August, September and October (0mm).

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Average snowfall days in September
Chicago, IL

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

The month with the highest number of snowfall days is January (10.6 days).
Months with the least snowfall days are June, July, August and September (0 days).

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Average sea temperature in September
Chicago, IL

Average sea temperature in September - Chicago, IL
  • Average sea temperature in September: 20.3°C

The best month for swimming (with the highest average sea temperature) is August (23.3°C).
The coldest month (with the lowest average sea temperature) is February (2.7°C).

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

Average daylight in September / Average sunshine in September - Chicago, 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: 9.1h

Months with the most sunshine are July and August (Average sunshine: 10.6h).
The month with the least sunshine is January (Average sunshine: 3.7h).

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Average sunshine days in September
Chicago, IL

Average sunshine days in September - Chicago, IL
  • Average sunshine days in September: 12.1 days

The month with the most sunshine days is December (15.5 days).
The month with the least sunshine days is July (9.3 days).

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Average UV index in September
Chicago, IL

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

Months with the highest UV index are 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
Chicago, IL

Average cloud cover in September - Chicago, IL
  • Average cloud cover in September: 30

The month with the most cloud cover is January (Cloud cover 62).
Months with the least cloud cover are July and August (Cloud cover 27).

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Average visibility in September
Chicago, IL

Average visibility in September - Chicago, IL
  • Average visibility in September: 10km

Months with the highest visibility are September and October (10km).
Months with the lowest visibility are January, February, March, April, May, June, July, August, November and December (9km).

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