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Weather in September in Illinois

Thinking about venturing to Illinois this September and curious about the weather conditions to expect? This page holds all the key information you seek, responding to your question:

What is the weather like in Illinois in September?

Illinois is a region in the United States of America. September in Illinois generally has temperatures that range from pleasant to warm, with precipitation levels ranging from moderate to high.

Temperatures

During the day temperatures vary from pleasant in Roscoe at 21°C to warm in Metropolis at 28°C. At night it cools down to 15°C in Metropolis and 9°C in Roscoe.

Precipitation

In September, precipitation varies across different areas. From moderate rainfall in Freeport with an average of 70 mm to high rainfall in Roscoe with 124 mm.

Average sunshine

Meanwhile, Chicago enjoys approximately 226 hours of sunshine, offering a mostly sunny climate that adds a pleasant and vibrant feel to the month.

To learn more about the conditions in specific areas of Illinois in September, check out the map below. For more details on the yearly weather, visit our Illinois climate page.

Where to go in Illinois in September

Find more information for the most popular destinations in the Illinois on the map below. Click on a destination dot for more detailes.

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Legend perfect weather pleasant tolerable unpleasant poor
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C and 29°C and not too much precipitation (less than 90 mm a month).

Popular destinations

What is the weather like in September for the 5 most popular destinations in Illinois?

Chicago

In September Chicago generally has high temperatures with maximum daytime temperatures around 24°C, minimum nighttime temperatures around 14°C and moderate monthly rainfall. So on average the conditions are perfect that month.

Chicago
minimum temparatureMax temperature minimum temparatureMax temp
maximum temparatureMin temperature maximum temparatureMin temp
sun hoursMonthly sun hours sun hoursSun hours
precipitationMonthly rainfall precipitationRainfall
rain daysMonthly rainy days rain daysRainy days
conditionsWeather conditions conditionsWeather
<<   August August
<<  
28°C 
18°C 
280 hours 
115 mm 
11 days 
24°C 
14°C 
226 hours 
95 mm 
9 days 
October   >> October
>>  
17°C 
7°C 
195 hours 
76 mm 
12 days 
Climate in Chicago

Schaumburg

In September Schaumburg generally has high temperatures with maximum daytime temperatures around 24°C, minimum nighttime temperatures around 12°C and high monthly rainfall. So on average the conditions are pleasant that month.

Schaumburg
minimum temparatureMax temperature minimum temparatureMax temp
maximum temparatureMin temperature maximum temparatureMin temp
sun hoursMonthly sun hours sun hoursSun hours
precipitationMonthly rainfall precipitationRainfall
rain daysMonthly rainy days rain daysRainy days
conditionsWeather conditions conditionsWeather
<<   August August
<<  
28°C 
17°C 
280 hours 
121 mm 
11 days 
24°C 
12°C 
226 hours 
100 mm 
9 days 
October   >> October
>>  
17°C 
5°C 
195 hours 
74 mm 
12 days 
Climate in Schaumburg

Rosemont

In September Rosemont generally has high temperatures with maximum daytime temperatures around 24°C, minimum nighttime temperatures around 14°C and moderate monthly rainfall. So on average the conditions are perfect that month.

Rosemont
minimum temparatureMax temperature minimum temparatureMax temp
maximum temparatureMin temperature maximum temparatureMin temp
sun hoursMonthly sun hours sun hoursSun hours
precipitationMonthly rainfall precipitationRainfall
rain daysMonthly rainy days rain daysRainy days
conditionsWeather conditions conditionsWeather
<<   August August
<<  
28°C 
18°C 
280 hours 
115 mm 
11 days 
24°C 
14°C 
226 hours 
96 mm 
9 days 
October   >> October
>>  
17°C 
7°C 
195 hours 
78 mm 
11 days 
Climate in Rosemont

Joliet

In September Joliet generally has high temperatures with maximum daytime temperatures around 25°C, minimum nighttime temperatures around 13°C and moderate monthly rainfall. So on average the conditions are perfect that month.

Joliet
minimum temparatureMax temperature minimum temparatureMax temp
maximum temparatureMin temperature maximum temparatureMin temp
sun hoursMonthly sun hours sun hoursSun hours
precipitationMonthly rainfall precipitationRainfall
rain daysMonthly rainy days rain daysRainy days
conditionsWeather conditions conditionsWeather
<<   August August
<<  
28°C 
17°C 
280 hours 
131 mm 
12 days 
25°C 
13°C 
226 hours 
94 mm 
10 days 
October   >> October
>>  
17°C 
6°C 
195 hours 
83 mm 
11 days 
Climate in Joliet

Naperville

In September Naperville generally has high temperatures with maximum daytime temperatures around 25°C, minimum nighttime temperatures around 12°C and moderate monthly rainfall. So on average the conditions are perfect that month.

Naperville
minimum temparatureMax temperature minimum temparatureMax temp
maximum temparatureMin temperature maximum temparatureMin temp
sun hoursMonthly sun hours sun hoursSun hours
precipitationMonthly rainfall precipitationRainfall
rain daysMonthly rainy days rain daysRainy days
conditionsWeather conditions conditionsWeather
<<   August August
<<  
28°C 
17°C 
280 hours 
112 mm 
11 days 
25°C 
12°C 
226 hours 
87 mm 
9 days 
October   >> October
>>  
17°C 
5°C 
195 hours 
82 mm 
11 days 
Climate in Naperville

Is your destination not in the list? Have a look at other destinations in Illinois, in the United States of America.

Is September the best time to visit Illinois?

We consider September to be one of the best times to travel to Illinois. Typically, the climate in Chicago is perfect. However, the weather conditions may vary depending on your destination.

Generally speaking, September provides perfect weather in Chicago. On the other hand, the weather in January, February, March, November and December tend to be poor.

Interested in more climate information?

We have much more information about the climate in Illinois. Interested in the weather conditions in a specific month? Select the month below.

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  • Weather and climate has detailed information for every country in the world. Are you going to the United States of America? Get detailed historical weather averages for many cities in the United States of America.

    Not sure yet where to go? We now have a tool which recommends destinations that suit your ideal travel conditions. Find out where to go with our weather planner.