Normal weather for Illinois in September
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.
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.
Illinois in September |
New York | ||
|---|---|---|---|
 Average Temperature |
27°C | 27°C | |
 High Temp |
30°C | 31°C | |
| Low Temp |
23°C | 21°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. You can expect regular precipitation, but there will also be some sunny days in the early part of the month.
With the temperature difference between day and night, it’s smart to wear layers. For the daytime, light clothing like shorts or a dress, and a hat and sunglasses are perfect. For the evening and morning, a shirt, maybe a light sweater, and thin pants are recommended.
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.
Since it cools down at night, it’s a good idea to wear layers. For the daytime, light clothing like shorts or a dress, and a hat and sunglasses are perfect. For the evening and morning, a shirt, maybe a light sweater, and thin pants are recommended.
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.
Because temperatures drop in the evening, wearing layers is recommended. For the daytime, light clothing like shorts or a dress, and a hat and sunglasses are perfect. For the evening and morning, a shirt, maybe a light sweater, and thin pants are recommended.
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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.
Is September a good time to visit Illinois?
Looking for great weather? September is a good time to be in Illinois. The temperatures are nice, and there’s not too much rain.
Temperature records for Illinois in September
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.
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Daily Temperature in September in Illinois
This chart shows the average daily high and low temperatures in September for Illinois, in degrees Celsius. The red line represents the highs, and the blue line shows the lows. The days of the month are displayed at the bottom of the chart. The data, based on historical observations, provide the average temperatures for this month.
Daily Precipitation in September in Illinois
The chart below shows the average daily precipitation in September for Illinois, measured in millimeters over the past few years. Precipitation is always measured as water, even if it’s snow or hail. The days of the month are listed at the bottom of the chart.
A low average precipitation means that the chance of rain on that day is usually small, while a higher average suggests that it rained more often. But remember, it’s just an average, and every day can be different. Based on historical weather data for September, you can expect about 12 days of precipitation in Illinois.
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.
Temperature in September in Illinois Over the Years
This chart shows the average temperature in September in Illinois, measured in degrees Celsius, over the past few years.
Total Precipitation in September in Illinois Over the Years
This chart shows the average precipitation in September in Illinois, measured in millimeters over the past years. Precipitation is always measured as water, whether it’s snow or hail.
Daily Climate 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.
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.
