Chicago

Illinois Weather in September

Average temperatures, rainfall, sunshine and the best places to visit in Illinois, the United States of America in September.

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Chicago Schaumburg Rosemont Joliet

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

What to Expect in Illinois in September

Illinois, the United States of America 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 (70°F) to warm in Metropolis at 28°C (82°F). At night it cools down to 15°C (59°F) in Metropolis and 9°C (48°F) in Roscoe.

For a closer look at conditions across Illinois, the United States of America, refer to the map below.

Precipitation

In September, precipitation varies across different areas. From moderate rainfall in Freeport with an average of 70 mm (2.8 in) to high rainfall in Roscoe with 124 mm (4.9 in).

Average sunshine

Most destinations offer generous amounts of sunshine this September. For example, Chicago gets approximately 226 hours of sunlight, perfect for anyone wanting bright, sunny days.

Explore Illinois by month

Pick a month to see the average temperature, rainfall and sunshine in Illinois — and find the best time to visit. (based on Chicago)

January-1°C (30°F) February0°C (32°F) March8°C (46°F) April15°C (59°F) May21°C (70°F) June26°C (79°F) This monthJuly29°C (84°F) August28°C (82°F) September24°C (75°F) October17°C (63°F) November9°C (48°F) December3°C (37°F)
Best Time to Visit Illinois →

Best Places to Visit in Illinois in September

Click on a destination dot for more details. Toggle the map to compare temperatures or precipitation across Illinois.

Conditions Temperatures Precipitation
perfect weather
pleasant
tolerable
unpleasant
poor

Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).

Popular Destinations in Illinois

What is the weather like in September for some of the most popular destinations in Illinois, the United States of America?

Temperature range in Illinois (September)

Precipitation variation in Illinois (September)

Chicago

In September Chicago generally has high temperatures with maximum daytime temperatures around 24°C (75°F), minimum nighttime temperatures around 14°C (57°F) and moderate monthly rainfall. So on average the conditions are perfect that month.

« August
September
October »
August
September
October
Max temperature
28°C (82°F)
24°C (75°F)
17°C (63°F)
Min temperature
18°C (64°F)
14°C (57°F)
7°C (45°F)
Monthly sun hours
280 hours
226 hours
195 hours
Monthly rainfall
115 mm (4.5 in)
95 mm (3.7 in)
76 mm (3 in)
Monthly rainy days
11 days
9 days
12 days
Weather conditions
pleasant
perfect
tolerable
Climate in Chicago →

Schaumburg

In September Schaumburg generally has high temperatures with maximum daytime temperatures around 24°C (75°F), minimum nighttime temperatures around 12°C (54°F) and high monthly rainfall. So on average the conditions are pleasant that month.

« August
September
October »
August
September
October
Max temperature
28°C (82°F)
24°C (75°F)
17°C (63°F)
Min temperature
17°C (63°F)
12°C (54°F)
5°C (41°F)
Monthly sun hours
280 hours
226 hours
195 hours
Monthly rainfall
121 mm (4.8 in)
100 mm (3.9 in)
74 mm (2.9 in)
Monthly rainy days
11 days
9 days
12 days
Weather conditions
pleasant
pleasant
tolerable
Climate in Schaumburg →

Rosemont

In September Rosemont generally has high temperatures with maximum daytime temperatures around 24°C (75°F), minimum nighttime temperatures around 14°C (57°F) and moderate monthly rainfall. So on average the conditions are perfect that month.

« August
September
October »
August
September
October
Max temperature
28°C (82°F)
24°C (75°F)
17°C (63°F)
Min temperature
18°C (64°F)
14°C (57°F)
7°C (45°F)
Monthly sun hours
280 hours
226 hours
195 hours
Monthly rainfall
115 mm (4.5 in)
96 mm (3.8 in)
78 mm (3.1 in)
Monthly rainy days
11 days
9 days
11 days
Weather conditions
pleasant
perfect
tolerable
Climate in Rosemont →

Joliet

In September Joliet generally has high temperatures with maximum daytime temperatures around 25°C (77°F), minimum nighttime temperatures around 13°C (55°F) and moderate monthly rainfall. So on average the conditions are perfect that month.

« August
September
October »
August
September
October
Max temperature
28°C (82°F)
25°C (77°F)
17°C (63°F)
Min temperature
17°C (63°F)
13°C (55°F)
6°C (43°F)
Monthly sun hours
280 hours
226 hours
195 hours
Monthly rainfall
131 mm (5.2 in)
94 mm (3.7 in)
83 mm (3.3 in)
Monthly rainy days
12 days
10 days
11 days
Weather conditions
pleasant
perfect
tolerable
Climate in Joliet →

Naperville

In September Naperville generally has high temperatures with maximum daytime temperatures around 25°C (77°F), minimum nighttime temperatures around 12°C (54°F) and moderate monthly rainfall. So on average the conditions are perfect that month.

« August
September
October »
August
September
October
Max temperature
28°C (82°F)
25°C (77°F)
17°C (63°F)
Min temperature
17°C (63°F)
12°C (54°F)
5°C (41°F)
Monthly sun hours
280 hours
226 hours
195 hours
Monthly rainfall
112 mm (4.4 in)
87 mm (3.4 in)
82 mm (3.2 in)
Monthly rainy days
11 days
9 days
11 days
Weather conditions
pleasant
perfect
tolerable
Climate in Naperville →

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

Popular cities in September

Day & night temperatures, rainfall and average weather in Illinois in September.

City Weather Day temp Night temp Rainfall
Chicago 24°C (75°F) 14°C (57°F) 95 mm (3.7 in)
Schaumburg 24°C (75°F) 12°C (54°F) 100 mm (3.9 in)
Rosemont 24°C (75°F) 14°C (57°F) 96 mm (3.8 in)
Joliet 25°C (77°F) 13°C (55°F) 94 mm (3.7 in)
Naperville 25°C (77°F) 12°C (54°F) 87 mm (3.4 in)
Waukegan 22°C (72°F) 13°C (55°F) 94 mm (3.7 in)

Illinois weather in September: frequently asked questions

What is the weather like in Illinois, the United States of America in September?

In September, Illinois, the United States of America generally has perfect weather conditions. Chicago sees daytime temperatures near 24°C (75°F), with nights cooling to roughly 14°C (57°F).

What is the average temperature in Illinois, the United States of America in September?

In Chicago, the average daytime high in September is 24°C (75°F), while nighttime temperatures drop to around 14°C (57°F).

Does Illinois, the United States of America get a lot of rain in September?

September is on the drier side in Illinois, the United States of America. Chicago averages only about 95 mm (3.7 in), with most days staying dry.

Is September a Good Time to Visit Illinois, the United States of America?

We consider September to be one of the best times to travel to Illinois, the United States of America. 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.

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.

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