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 introduction of September notes a subtle temperature variation to a still moderately hot 77°F (25°C) from August's 81.1°F (27.3°C). The low-temperature averages to a moderate 58.5°F (14.7°C) during the nights of September.Humidity
In Decatur, the average relative humidity in September is 76%.Rainfall
In Decatur, in September, it is raining for 10.6 days, with typically 1.18" (30mm) of accumulated precipitation. Throughout the year, there are 130.2 rainfall days, and 16.34" (415mm) of precipitation is accumulated.Snowfall
In Decatur, Illinois, snow does not fall in May through October.Daylight
In Decatur, the average length of the day in September is 12h and 26min.On the first day of September, sunrise is at 6:24 am and sunset at 7:26 pm. On the last day of the month, sunrise is at 6:51 am and sunset at 6:39 pm CDT.
Sunshine
In September, the average sunshine in Decatur is 9.2h.UV index
The average daily maximum UV index in September in Decatur is 5. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for the ordinary person.Note: The maximum UV index of 5 during September leads to these instructions:
Take measures. Individuals with light skin might experience burns in under 30 minutes. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. Protect your eyes, ears, face, and neck from the Sun by wearing a wide-brimmed hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the usual temperature for Decatur in September?
What is the average humidity in September in Decatur?
How much does it rain in Decatur in September?
When it does not snow in Decatur?
How many hours of daylight does Decatur have in September?
What time are sunrise and sunset in September in Decatur?
How long on average sun shines in September in Decatur?
What is the UV index intensity in September in Decatur?
Average temperature in September
Decatur, IL
- Average high temperature in September: 77°F
The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (32.9°F).
- Average low temperature in September: 58.5°F
The month with the highest average low temperature is July (65.7°F).
The coldest month (with the lowest average low temperature) is January (21.2°F).
Average pressure in September
Decatur, IL
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in September
Decatur, IL
- Average wind speed in September: 7.2mph
The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (6.3mph).
Average humidity in September
Decatur, IL
- Average humidity in September: 76%
The month with the highest relative humidity is July (84%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
Decatur, IL
- Average rainfall in September: 1.18"
The wettest month (with the highest rainfall) is May (2.01").
The driest months (with the least rainfall) are February and December (0.87").
Average rainfall days in September
Decatur, IL
- Average rainfall days in September: 10.6 days
The month with the highest number of rainy days is May (17 days).
The month with the least rainy days is February (5.8 days).
Average snowfall in September
Decatur, IL
- Average snowfall in September: 0"
The month with the highest snowfall is January (1.85").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Decatur, IL
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (7.2 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Decatur, IL
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 9h and 1min
The month with the most sunshine is June (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 6min).
Average sunshine days in September
Decatur, IL
- Average sunshine days in September: 17.3 days
The month with the most sunshine days is October (19.8 days).
The month with the least sunshine days is May (11.5 days).
Average UV index in September
Decatur, IL
- Average UV index in September: 5
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Decatur, IL
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 56).
The month with the least cloud cover is September (Cloud cover 29).
Average visibility in September
Decatur, 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).
Decatur, Illinois, USA
Weather forecast for your location
2. Allow the app to use your location