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United StatesThe weather in September in Illinois
It's warm in September in Illinois with an average temperature of 27°C. Temperatures this month range from a low of 23°C to a high of 30°C. At night, you can expect temperatures between 12°C and 19°C.
Looking for great weather? September is a good time to be in Illinois. The temperatures are nice, and there’s not too much rain.
Average temperatures and precipitation
This chart shows the average daily maximum and minimum temperatures (in degrees Celsius) and precipitation (in millimeters) in September for Illinois, United States. A low precipitation value usually indicates little to no rainfall on that day in recent years, while a higher value suggests more frequent rainfall.
Temperature records
With 36°C in 2015, Illinois reached the highest temperature in September over the past 10 years. The lowest daytime temperature in this month was 12°C in 2014. The extreme nighttime temperatures ranged from a lowest recorded value of 4°C to a highest value of 24°C.
Rainfall amount
In September, there is an average of 82 mm of precipitation, spread over 12 days. The wind speed is around 4 Bft, mostly coming from the South.
Daily weather in September for Illinois
Click on any day in September to get detailed info about the usual weather on that day in Illinois. Check out the historical temperatures and precipitation over the past 10 years on this day.
September weather comparison
| Illinois | New York | |
|---|---|---|
| Average temperature | 27°C | 27°C |
| Max. temperature | 30°C | 31°C |
| Min. temperature | 12°C | -5°C |
| Total precipitation | 82 mm | 57 mm |
| Rainy days | 12 days | 9 days |
Start of September
The month of September starts in Illinois with hot temps, averaging around 28°C during the day and nights around 18°C.
Mid September
By mid-September, daytime temps stay steady at around 28°C, with nights around 16°C. There’s a chance of some showers during this time, but plenty of dry and sunny days too.
End of September
By the end of September, the average daytime temperature in Illinois is around 26°C, while nighttime temps are about 15°C. A shower might pop up, but overall, the weather will be dry and sunny.
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UV index
The UV index is a maximum of 5 this month. That's a moderate value on the intensity scale of 1 to 11. Unprotected skin can burn in about 30 minutes.
Check out the climate of Illinois for all months and discover the best travel time
The climate in Illinois is based on weather data from . Other places, like New York City, Miami or Los Angeles, might have different weather. You can check out all destinations in Illinois to get the full picture of the climate.
Temperature charts
These charts show the average temperatures in September in Illinois, United States. The temperatures are shown in degrees Celsius and are calculated based on data from the past 10 years.
Daily Temperature in September in Illinois
Temperature in September in Illinois over the years
Precipitation charts
These charts show the average amount of precipitation in September in Illinois, United States. Precipitation is always measured as water, even when it falls as snow or hail The amount of precipitation is displayed in millimeters, while snowfall is shown in centimeters.
Daily Precipitation in September in Illinois
Total precipitation in September in Illinois over the years
Daily UV index in September in Illinois
This chart shows the average daily UV index in September in Illinois, with the UV index ranging from 0 to a maximum of 11. The bottom of the chart shows the days of the month. Based on historical data, this chart provides an idea of the daily UV radiation levels you can expect.
Weather experiences in September in Illinois
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Average weather in Illinois by month
Click on a month below to see detailed weather info for Illinois. Based on historical weather data, you can see the average temperature, precipitation, wind, and UV index for each day of the month.