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
The onset of September manifests an average high-temperature of a still warm 77.7°F (25.4°C), demonstrating a minor variation from the preceding month. In Clayton, September nights witness a steady temperature drop to a refreshing 58.1°F (14.5°C).Humidity
The average relative humidity in September is 75%.Rainfall
In September, the rain falls for 10.2 days. Throughout September, 2.2" (56mm) of precipitation is accumulated. Throughout the year, there are 132 rainfall days, and 22.17" (563mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
In Clayton, the average length of the day in September is 12h and 26min.On the first day of September, sunrise is at 6:32 am and sunset at 7:34 pm. On the last day of the month, sunrise is at 6:59 am and sunset at 6:47 pm CDT.
Sunshine
In September, the average sunshine is 9.4h.UV index
The average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a medium vulnerability from unprotected exposure to Sun's UV rays for the ordinary person.Note: The UV index of 5 during September leads to these advisories:
Guard yourself - Avoiding sunburn is suggested. The midday Sun can be dangerous due to its intense radiation; always find shade and reduce exposure. On sunny days, it's ideal to wear sunglasses that filter out UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in September?
What is the average humidity in September?
How many days does it rain in September?
When it does not snow?
What is the average length of the day in September in Clayton?
When is the sunrise / sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September?
Average temperature in September
Clayton, IL
- Average high temperature in September: 77.7°F
The warmest month (with the highest average high temperature) is July (83.7°F).
The month with the lowest average high temperature is January (32.7°F).
- Average low temperature in September: 58.1°F
The month with the highest average low temperature is July (66.6°F).
The coldest month (with the lowest average low temperature) is January (20.3°F).
Average pressure in September
Clayton, IL
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Clayton, IL
- Average wind speed in September: 7.1mph
The windiest month (with the highest average wind speed) is January (10.2mph).
The calmest month (with the lowest average wind speed) is July (6.3mph).
Average humidity in September
Clayton, IL
- Average humidity in September: 75%
The month with the highest relative humidity is July (82%).
The month with the lowest relative humidity is October (71%).
Average rainfall in September
Clayton, IL
- Average rainfall in September: 2.2"
The wettest month (with the highest rainfall) is May (3.23").
The driest month (with the least rainfall) is January (0.98").
Average rainfall days in September
Clayton, IL
- Average rainfall days in September: 10.2 days
The month with the highest number of rainy days is May (16.9 days).
The months with the least rainy days are January and February (5.3 days).
Average snowfall in September
Clayton, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.19").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Clayton, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (7.8 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Clayton, IL
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 9h and 2min
The months with the most sunshine are June and July (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 4h and 18min).
Average sunshine days in September
Clayton, IL
- Average sunshine days in September: 18.2 days
The month with the most sunshine days is January (20 days).
The month with the least sunshine days is May (11.4 days).
Average UV index in September
Clayton, IL
- Average UV index in September: 5
The months with the highest UV index are 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
Clayton, IL
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 54).
The months with the least cloud cover are July, August and September (Cloud cover 30).
Average visibility in September
Clayton, 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).
Clayton, Illinois, USA
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