September weather forecastRock Falls, IL
September
Weather in September
September, the first month of the autumn in Rock Falls, is still a warm month, with temperature in the range of an average high of 73.9°F (23.3°C) and an average low of 55.2°F (12.9°C).Temperature
In September, the meteorological conditions change slightly, with the average high-temperature moving from 79.3°F (26.3°C) in August to a still moderately hot 73.9°F (23.3°C). Nighttime temperature experiences an average drop to a fresh 55.2°F (12.9°C) in September.Humidity
The average relative humidity in September is 78%.Rainfall
In Rock Falls, during September, the rain falls for 9.7 days and regularly aggregates up to 1.26" (32mm) of precipitation. Throughout the year, there are 130.2 rainfall days, and 17.36" (441mm) of precipitation is accumulated.Snowfall
In Rock Falls, snow does not fall in May through September.Daylight
The average length of the day in September in Rock Falls is 12h and 28min.On the first day of September, sunrise is at 6:25 am and sunset at 7:31 pm. On the last day of the month, sunrise is at 6:55 am and sunset at 6:41 pm CDT.
Sunshine
In Rock Falls, the average sunshine in September is 9.1h.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 unsafe exposure to UV radiation for average individuals.Note: In September, a regular UV index of 4 translates into these guidelines:
Ensure safety - Sun damage prevention is strongly urged. Considering the harmful UV rays from the Sun during midday, it's essential to reduce 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
Rock Falls, IL
- Average high temperature in September: 73.9°F
The warmest month (with the highest average high temperature) is July (80.2°F).
The month with the lowest average high temperature is January (27.7°F).
- Average low temperature in September: 55.2°F
The month with the highest average low temperature is July (63.9°F).
The coldest month (with the lowest average low temperature) is January (14.9°F).
Average pressure in September
Rock Falls, IL
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.12"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Rock Falls, IL
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is April (10.4mph).
The calmest month (with the lowest average wind speed) is August (6.4mph).
Average humidity in September
Rock Falls, IL
- Average humidity in September: 78%
The months with the highest relative humidity are January and July (85%).
The month with the lowest relative humidity is October (73%).
Average rainfall in September
Rock Falls, IL
- Average rainfall in September: 1.26"
The wettest month (with the highest rainfall) is May (2.83").
The driest months (with the least rainfall) are January and February (0.75").
Average rainfall days in September
Rock Falls, IL
- Average rainfall days in September: 9.7 days
The month with the highest number of rainy days is May (17.3 days).
The month with the least rainy days is January (4.8 days).
Average snowfall in September
Rock Falls, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.56").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Rock Falls, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (10.2 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
Rock Falls, 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 6min
The month with the most sunshine is July (Average sunshine: 9h and 48min).
The month with the least sunshine is January (Average sunshine: 3h and 48min).
Average sunshine days in September
Rock Falls, IL
- Average sunshine days in September: 18.4 days
The months with the most sunshine days are November and December (18.8 days).
The month with the least sunshine days is June (11.3 days).
Average UV index in September
Rock Falls, IL
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The month with the lowest UV index is December (UV index 1).
Average cloud cover in September
Rock Falls, IL
- Average cloud cover in September: 31
The month with the most cloud cover is January (Cloud cover 60).
The month with the least cloud cover is September (Cloud cover 31).
Average visibility in September
Rock Falls, IL
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are July and August (5mi).
