September weather forecastRiver Forest, IL
September
Weather in September
September, the first month of the autumn in River Forest, is still a pleasant month, with an average temperature fluctuating between 60.4°F (15.8°C) and 72.1°F (22.3°C).Temperature
The beginning of September brings a minor change in the average high-temperature, shifting from a warm 79.3°F (26.3°C) in August to an agreeable 72.1°F (22.3°C). In River Forest, the September nights cool down to an average low of 60.4°F (15.8°C).Humidity
In September, the average relative humidity is 74%.Rainfall
In September, the rain falls for 14.5 days. Throughout September, 2.72" (69mm) of precipitation is accumulated. Throughout the year, there are 157.8 rainfall days, and 33.7" (856mm) of precipitation is accumulated.Snowfall
June through September are months without snowfall.Daylight
The average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:17 am and sunset at 7:24 pm. On the last day of September, sunrise is at 6:47 am and sunset at 6:34 pm CDT.
Sunshine
The average sunshine in September is 9h.UV index
In River Forest, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for ordinary individuals.Note: A daily maximum UV index of 4 in September translates into the following instructions:
Be mindful. Those with pale skin might receive burns in fewer than 30 minutes. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. A hat with a broad brim is indispensable, filtering out up to half of UV rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
River Forest, IL
- Average high temperature in September: 72.1°F
The warmest month (with the highest average high temperature) is July (79.7°F).
The month with the lowest average high temperature is January (28.9°F).
- Average low temperature in September: 60.4°F
The month with the highest average low temperature is July (67.5°F).
The coldest month (with the lowest average low temperature) is January (19.4°F).
Average pressure in September
River Forest, 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
River Forest, IL
- Average wind speed in September: 8.3mph
The windiest month (with the highest average wind speed) is January (11.1mph).
The calmest months (with the lowest average wind speed) are July and August (7mph).
Average humidity in September
River Forest, IL
- Average humidity in September: 74%
The month with the highest relative humidity is January (82%).
The month with the lowest relative humidity is October (72%).
Average rainfall in September
River Forest, IL
- Average rainfall in September: 2.72"
The wettest month (with the highest rainfall) is May (4.49").
The driest month (with the least rainfall) is December (1.57").
Average rainfall days in September
River Forest, IL
- Average rainfall days in September: 14.5 days
The month with the highest number of rainy days is May (18.8 days).
The month with the least rainy days is February (5.1 days).
Average snowfall in September
River Forest, IL
- Average snowfall in September: 0"
The month with the highest snowfall is February (4.69").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
River Forest, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (10.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
River Forest, IL
- Average daylight in September: 12h and 30min
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: 9h and 0min
The month with the most sunshine is August (Average sunshine: 10h and 36min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in September
River Forest, IL
- Average sunshine days in September: 13.4 days
The month with the most sunshine days is December (16.7 days).
The month with the least sunshine days is July (9.9 days).
Average UV index in September
River Forest, 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
River Forest, IL
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 27).
Average visibility in September
River Forest, 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).
