Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
O'Fallon's average high-temperature in September is a still warm 79°F (26.1°C), marking an insignificant difference from the 84.2°F (29°C) of August. September nights are marked by an average low-temperature of 60.3°F (15.7°C).Humidity
In O'Fallon, the average relative humidity in September is 75%.Rainfall
In O'Fallon, in September, during 9.8 rainfall days, 0.67" (17mm) of precipitation is typically accumulated. Throughout the year, there are 108.8 rainfall days, and 10.24" (260mm) of precipitation is accumulated.Snowfall
April through October are months without snowfall.Daylight
In O'Fallon, the average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:29 am and sunset at 7:29 pm. On the last day of the month, sunrise is at 6:55 am and sunset at 6:43 pm CDT.
Sunshine
In O'Fallon, the average sunshine in September is 9.3h.UV index
In September, the average daily maximum UV index is 5. A UV Index of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV radiation for the average person.Note: The daily maximum UV index of 5 in September interprets into the following advice:
Take necessary precautions - Suggestions to elude sunburn are provided. Avoiding direct sunlight during midday hours helps reduce the risk from intense UV radiation. During bright days, sunglasses that offer UVA and UVB defense are recommended.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the usual temperature for O'Fallon in September?
What is the average humidity in September in O'Fallon?
How much does it rain in September?
When it does not snow?
What is the average length of the day in September?
When are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September?
Average temperature in September
O'Fallon, IL
- Average high temperature in September: 79°F
The warmest month (with the highest average high temperature) is July (85.6°F).
The month with the lowest average high temperature is January (37.8°F).
- Average low temperature in September: 60.3°F
The month with the highest average low temperature is July (68.2°F).
The coldest month (with the lowest average low temperature) is January (24.6°F).
Average pressure in September
O'Fallon, IL
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
O'Fallon, IL
- Average wind speed in September: 6.2mph
The windiest month (with the highest average wind speed) is January (9.5mph).
The calmest month (with the lowest average wind speed) is July (5.6mph).
Average humidity in September
O'Fallon, IL
- Average humidity in September: 75%
The months with the highest relative humidity are May, July and August (79%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
O'Fallon, IL
- Average rainfall in September: 0.67"
The wettest month (with the highest rainfall) is July (1.42").
The driest month (with the least rainfall) is December (0.31").
Average rainfall days in September
O'Fallon, IL
- Average rainfall days in September: 9.8 days
The month with the highest number of rainy days is July (13.1 days).
The month with the least rainy days is December (4.6 days).
Average snowfall in September
O'Fallon, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (0.51").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
O'Fallon, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (4.7 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
O'Fallon, IL
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in September: 9h and 2min
The months with the most sunshine are June and July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 30min).
Average sunshine days in September
O'Fallon, IL
- Average sunshine days in September: 18.3 days
The month with the most sunshine days is December (23.6 days).
The months with the least sunshine days are May and July (15.5 days).
Average UV index in September
O'Fallon, IL
- Average UV index in September: 5
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
O'Fallon, IL
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in September
O'Fallon, IL
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
O'Fallon, Illinois, USA
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