September weather forecastDowners Grove, IL
September
Weather in September
September in Downers Grove marks the onset of fall, with a decrease in temperature from August. The month begins to reel back the long days of summer, replacing them with shorter daylight hours of 12.5. It further transitions the weather pattern by producing slightly less rainfall than August. A rise in wind speed indicates the arrival of crispier autumn days following the waning summer heat. The humidity and pressure levels hold steady, setting a comfortable atmosphere for the residents.Temperature
September's onset in Downers Grove, Illinois, introduces a mild reduction in the average high-temperature, from a warm 81.1°F (27.3°C) in August to a still moderately hot 74.3°F (23.5°C). Downers Grove anticipates an average minimum temperature of 57.9°F (14.4°C) in the month of September.Humidity
In September, the average relative humidity is 75%.Rainfall
In Downers Grove, in September, during 11.5 rainfall days, 1.18" (30mm) of precipitation is typically accumulated. Throughout the year, there are 118.5 rainfall days, and 13.74" (349mm) of precipitation is accumulated.Snowfall
May through September are months without snowfall in Downers Grove.Daylight
In September, the average length of the day is 12h and 28min.On the first day of the month, sunrise is at 6:18 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 Downers Grove, the average sunshine in September is 8.7h.UV index
The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for the ordinary person.Note: The maximum UV index of 4 during September translates into these guidelines:
Be vigilant - Suggestions to stave off sun damage are provided. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Downers Grove, IL
- Average high temperature in September: 74.3°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (28.8°F).
- Average low temperature in September: 57.9°F
The month with the highest average low temperature is July (66.4°F).
The coldest month (with the lowest average low temperature) is January (17.1°F).
Average pressure in September
Downers Grove, 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
Downers Grove, IL
- Average wind speed in September: 7mph
The windiest month (with the highest average wind speed) is January (9.7mph).
The calmest month (with the lowest average wind speed) is August (6.1mph).
Average humidity in September
Downers Grove, 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
Downers Grove, IL
- Average rainfall in September: 1.18"
The wettest month (with the highest rainfall) is May (1.97").
The driest month (with the least rainfall) is December (0.63").
Average rainfall days in September
Downers Grove, IL
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is May (14.9 days).
The month with the least rainy days is February (4.2 days).
Average snowfall in September
Downers Grove, IL
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.28").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Downers Grove, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (9.7 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Downers Grove, 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 42min
The month with the most sunshine is August (Average sunshine: 10h and 0min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in September
Downers Grove, IL
- Average sunshine days in September: 16.1 days
The month with the most sunshine days is December (20.7 days).
The month with the least sunshine days is July (11.8 days).
Average UV index in September
Downers Grove, 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 January (UV index 1).
Average cloud cover in September
Downers Grove, IL
- Average cloud cover in September: 32
The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 31).
Average visibility in September
Downers Grove, 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).
