September weather forecast
Saint Charles, IL

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Weather in September

The first month of the autumn, September, is still a warm month in Saint Charles, Illinois, with an average temperature varying between 73.4°F (23°C) and 56.5°F (13.6°C).

Temperature

The shift from August to September includes a minor decrease in the average high-temperature, lightly dropping from a moderately hot 79.5°F (26.4°C) to a still warm 73.4°F (23°C). Saint Charles observes an average nighttime low-temperature of 56.5°F (13.6°C) during the month of September.

Humidity

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

Rainfall

In Saint Charles, Illinois, during September, the rain falls for 9.5 days and regularly aggregates up to 0.71" (18mm) of precipitation. In Saint Charles, Illinois, during the entire year, the rain falls for 101.9 days and collects up to 8.58" (218mm) of precipitation.

Snowfall

In Saint Charles, snow does not fall in May through September.

Daylight

In September, the average length of the day in Saint Charles is 12h and 28min.
On the first day of the month, sunrise is at 6:19 am and sunset at 7:26 pm. On the last day of September, in Saint Charles, sunrise is at 6:49 am and sunset at 6:36 pm CDT.

Sunshine

In Saint Charles, the average sunshine in September is 8.8h.

UV index

The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for average individuals.
Note: In September, a regular UV index of 4 translates into these guidelines:
Take necessary precautions - Defending against sun damage is advocated. Avoiding direct sun during mid-day hours can prevent harmful UV radiation exposure. To best shield against UV radiation, choose sun-safe garments and dependable sunglasses.
Updated: Feb 12, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are September temperatures in Saint Charles?

Saint Charles in September has an average high-temperature of 73.4°F (23°C) and an average low-temperature of 56.5°F (13.6°C). In July, the average heat index (a.k.a. 'apparent temperature', 'real feel'), which takes the relative humidity and factors it into the air temperature reading, is evaluated at 86°F (30°C).

What is the average humidity in September in Saint Charles?

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

How much does it rain in Saint Charles in September?

In September, in Saint Charles, Illinois, the rain falls for 9.5 days. Throughout September, 0.71" (18mm) of precipitation is accumulated.

When it does not snow in Saint Charles?

In Saint Charles, Illinois, snow does not fall in May through September.

Does it snow in Saint Charles in September?

In Saint Charles, Illinois, in September, it doesn't snow. In October, it regularly snows.

What is the average length of the day in September in Saint Charles?

The average day length in September is 12h and 28min.

When is the sunrise / sunset in September in Saint Charles?

In September, on the first day of the month, sunrise is at 6:19 am and sunset at 7:26 pm. On the last day of the month, in Saint Charles, sunrise is at 6:49 am and sunset at 6:36 pm CDT.

How many hours of sunshine does Saint Charles have in September?

The average sunshine duration in September is 8.8h.

What is the UV index intensity in September in Saint Charles?

In Saint Charles, Illinois, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium health risk from unsafe exposure to Sun's UV rays.
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
Saint Charles, IL

Average temperature in September - Saint Charles, IL
  • Average high temperature in September: 73.4°F

The warmest month (with the highest average high temperature) is July (81°F).
The month with the lowest average high temperature is January (27.9°F).

  • Average low temperature in September: 56.5°F

The month with the highest average low temperature is July (64.2°F).
The coldest month (with the lowest average low temperature) is January (16.2°F).

Average pressure in September
Saint Charles, IL

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

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

Average wind speed in September
Saint Charles, IL

Average wind speed in September - Saint Charles, IL
  • Average wind speed in September: 7.1mph

The windiest month (with the highest average wind speed) is January (9.9mph).
The calmest month (with the lowest average wind speed) is August (6.1mph).

Average humidity in September
Saint Charles, IL

Average humidity in September - Saint Charles, IL
  • Average humidity in September: 78%

The months with the highest relative humidity are January and February (83%).
The month with the lowest relative humidity is October (74%).

Average rainfall in September
Saint Charles, IL

Average rainfall in September - Saint Charles, IL
  • Average rainfall in September: 0.71"

The wettest month (with the highest rainfall) is May (1.26").
The driest months (with the least rainfall) are November and December (0.39").

Average rainfall days in September
Saint Charles, IL

Average rainfall days in September - Saint Charles, IL
  • Average rainfall days in September: 9.5 days

The month with the highest number of rainy days is May (12.4 days).
The month with the least rainy days is January (3.4 days).

Average snowfall in September
Saint Charles, IL

Average snowfall in September - Saint Charles, IL
  • Average snowfall in September: 0"

The month with the highest snowfall is January (1.14").
The months with the least snowfall are May, June, July, August and September (0").

Average snowfall days in September
Saint Charles, IL

Average snowfall days in September - Saint Charles, IL
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (7.6 days).
The months with the least snowfall days are June, July, August and September (0 days).

Average daylight in September /
Average sunshine in September
Saint Charles, IL

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

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

  • Average sunshine in September: 8h and 5min

The month with the most sunshine is July (Average sunshine: 9h and 54min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).

Average sunshine days in September
Saint Charles, IL

Average sunshine days in September - Saint Charles, IL
  • Average sunshine days in September: 17.7 days

The month with the most sunshine days is December (22.4 days).
The month with the least sunshine days is June (13.3 days).

Average UV index in September
Saint Charles, IL

Average UV index in September - Saint Charles, IL
  • Average UV index in September: 4

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

Average cloud cover in September
Saint Charles, IL

Average cloud cover in September - Saint Charles, IL
  • Average cloud cover in September: 32

The month with the most cloud cover is January (Cloud cover 62).
The month with the least cloud cover is September (Cloud cover 32).

Average visibility in September
Saint Charles, IL

Average visibility in September - Saint Charles, IL
  • Average visibility in September: 6mi

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

Saint Charles, Illinois, USA

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