September weather forecastDes Plaines, IL
September
Weather in September
September signals the onset of autumn in Des Plaines, mirroring a blend of summer's warmth and the chill of the upcoming winter. The noticeable dip in temperature from August's average high of 79.3°F (26.3°C) to September's 72.5°F (22.5°C) signifies the transition. The weather stays mostly agreeable as the greenery gives way to spectacular autumn hues. The transition from summer to autumn becomes more pronounced as October commences. September acts as a bridge, balancing the hot summer days with the cooler days of fall.Temperature
September's arrival comes with a mild decrease in the average high-temperature, moving subtly from a warm 79.3°F (26.3°C) in August to a pleasant 72.5°F (22.5°C). Throughout September nights, Des Plaines experiences a consistent temperature average of 59.7°F (15.4°C).Humidity
In Des Plaines, the average relative humidity in September is 74%.Rainfall
In Des Plaines, in September, it is raining for 14 days, with typically 2.48" (63mm) of accumulated precipitation. Throughout the year, there are 153.1 rainfall days, and 32.01" (813mm) of precipitation is accumulated.Snowfall
In Des Plaines, snow does not fall in June through September.Daylight
In Des Plaines, 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 6:48 am and sunset at 6:34 pm CDT.
Sunshine
In September, the average sunshine is 8.9h.UV index
The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for the ordinary person.Note: The UV index of 4 in September translates into these instructions:
Take necessary precautions - Defending against sun damage is advocated. During midday, the Sun's radiation is strongest, and it's advisable to reduce direct exposure. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Des Plaines, IL
- Average high temperature in September: 72.5°F
The warmest month (with the highest average high temperature) is July (80.6°F).
The month with the lowest average high temperature is January (28.8°F).
- Average low temperature in September: 59.7°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 (18.1°F).
Average pressure in September
Des Plaines, 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
Des Plaines, IL
- Average wind speed in September: 8.1mph
The windiest month (with the highest average wind speed) is January (10.8mph).
The calmest month (with the lowest average wind speed) is August (6.8mph).
Average humidity in September
Des Plaines, IL
- Average humidity in September: 74%
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
Des Plaines, IL
- Average rainfall in September: 2.48"
The wettest month (with the highest rainfall) is May (4.21").
The driest month (with the least rainfall) is December (1.5").
Average rainfall days in September
Des Plaines, IL
- Average rainfall days in September: 14 days
The month with the highest number of rainy days is May (18.5 days).
The month with the least rainy days is February (5.3 days).
Average snowfall in September
Des Plaines, IL
- Average snowfall in September: 0"
The month with the highest snowfall is February (4.84").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Des Plaines, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (10.6 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Des Plaines, 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: 8h and 54min
The months with the most sunshine are July and August (Average sunshine: 10h and 18min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in September
Des Plaines, IL
- Average sunshine days in September: 13.4 days
The months with the most sunshine days are November and December (16.9 days).
The month with the least sunshine days is April (10.4 days).
Average UV index in September
Des Plaines, 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
Des Plaines, IL
- Average cloud cover in September: 31
The month with the most cloud cover is January (Cloud cover 62).
The months with the least cloud cover are July and August (Cloud cover 29).
Average visibility in September
Des Plaines, 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).
