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 arrival of September suggests a slight decrease in the average high-temperature, moving from a warm 79.3°F (26.3°C) in August to a still moderately hot 73.8°F (23.2°C). Riverdale usually reports an average low-temperature of 59.2°F (15.1°C) during the month of September.Humidity
The average relative humidity in September is 75%.Rainfall
In Riverdale, in September, it is raining for 9.8 days, with typically 0.91" (23mm) of accumulated precipitation. Throughout the year, there are 110.3 rainfall days, and 10.31" (262mm) of precipitation is accumulated.Snowfall
May through September are months without snowfall.Daylight
In September, the average length of the day is 12h and 28min.On the first day of the month, sunrise is at 6:17 am and sunset at 7:23 pm. On the last day of September, in Riverdale, sunrise is at 6:47 am and sunset at 6:33 pm CDT.
Sunshine
In Riverdale, the average sunshine in September is 8.9h.UV index
In September, the average daily maximum UV index is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV radiation for average individuals.Note: A maximum high UV index of 4 in September translates into the following recommendations:
Guard yourself - Precautionary measures against sun damage are advocated. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. Using UVA and UVB-protective sunglasses and sun-protective clothing is effective against UV radiation.
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 much does it rain in September?
When it does not snow?
Does it snow in September?
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 reading in September?
Average temperature in September
Riverdale, IL
- Average high temperature in September: 73.8°F
The warmest month (with the highest average high temperature) is July (80.1°F).
The month with the lowest average high temperature is January (29.8°F).
- Average low temperature in September: 59.2°F
The month with the highest average low temperature is July (66.9°F).
The coldest month (with the lowest average low temperature) is January (19.6°F).
Average pressure in September
Riverdale, 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
Riverdale, IL
- Average wind speed in September: 8mph
The windiest month (with the highest average wind speed) is January (11mph).
The calmest months (with the lowest average wind speed) are July and August (6.8mph).
Average humidity in September
Riverdale, 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%).
Average rainfall in September
Riverdale, IL
- Average rainfall in September: 0.91"
The wettest months (with the highest rainfall) are May and June (1.38").
The driest months (with the least rainfall) are February and December (0.47").
Average rainfall days in September
Riverdale, IL
- Average rainfall days in September: 9.8 days
The month with the highest number of rainy days is July (14 days).
The month with the least rainy days is February (4.1 days).
Average snowfall in September
Riverdale, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (1.1").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Riverdale, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (9.3 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
Riverdale, IL
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 6min).
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 August (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 3h and 36min).
Average sunshine days in September
Riverdale, IL
- Average sunshine days in September: 16.9 days
The month with the most sunshine days is December (19.8 days).
The month with the least sunshine days is June (13.1 days).
Average UV index in September
Riverdale, 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 December (UV index 1).
Average cloud cover in September
Riverdale, IL
- Average cloud cover in September: 31
The month with the most cloud cover is January (Cloud cover 62).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in September
Riverdale, 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).
Riverdale, Illinois, USA
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