Chicago Weather in September

🇺🇸 United States

13°C

High

1°C

Low

Rain Days

Sunshine

65%

Humidity

North America › 🇺🇸 United States › Chicago

Updated: March 2026

Is September a Good Time to Visit Chicago?

5/10

Fair

September is a fair time to visit Chicago (5/10). Average highs of 13°C and 4 sunshine hours daily make conditions workable, though not exceptional. Culture-focused travellers and those who prefer lighter crowds will find September a practical choice, with prices running lower than peak May without sacrificing all the good weather. October offers a similar profile at lower hotel rates if dates are flexible. The main practical note: Chicago's popular sites are busiest between 10am and 3pm regardless of season. Arriving at opening time or after 4pm makes a significant difference to the experience. Planning tips: accommodation is generally available without long lead times, and flight prices are typically lower than peak season. Flexible travellers will find the best deals by booking 2-4 weeks ahead. Mid-week arrivals consistently unlock lower hotel rates than weekend check-ins.

vs August:19°C avg high

September weather in Chicago is defined by a daily temperature swing from 1°C at night to 13°C during the afternoon. Humidity averages 65%, and you can count on around 4 sunshine hours each day. That combination makes September warm and lush, though dressing in breathable fabrics keeps things manageable.

13°C

Avg High

1°C

Avg Low

4 days

Rain Days

Sunshine

65%

Humidity

Temperature in Chicago in September

The 12°C day-night temperature range is typical for continental climates: a light jacket in the morning that you shed by midday and need again after sunset. Humidity averages 65%, which is comfortable for most visitors. On warmer days, lighter fabrics help with the mild stickiness in the afternoon. UV index averages 6 this month, classed as moderate. Sunscreen is a sensible precaution for extended outdoor time, particularly at midday. Wind averages 15 km/h, light enough to be refreshing on warm days but noticeable in open coastal areas or elevated viewpoints. In Fahrenheit: 55°F average high, 34°F overnight low. Data sourced from Open-Meteo ERA5 climate reanalysis (1991–2020 normals).

Temperature in September

Monthly Precipitation (mm)

What to Wear in Chicago in September

Morning1°CBefore the day warms up

Afternoon13°CPeak daytime temperature

Evening4°CAfter sunset cools down

Packing for Chicago in September means dressing for 13°C days and 1°C evenings. A mid-weight jacket over a sweater handles 13°C daytime temperatures; the combination stays comfortable all day without overheating. Evenings drop 12°C to around 1°C, a notable shift that catches underprepared visitors off guard. Pack a dedicated evening layer. Comfortable walking trainers are the versatile choice for both outdoor sightseeing and indoor venues.

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Local tip: Layers are more practical than a single heavy garment in Chicago. The day-to-evening temperature shift rewards packing a versatile mid-layer you can add or remove as conditions change.

Events in Chicago in September

September has no major festivals or public holidays in Chicago, which is one of its practical advantages for independent travellers. Attractions run at lower capacity than during peak event periods, queues are shorter, and accommodation is easier to find without needing to book many months in advance. Local restaurants, markets, and transport operate at a relaxed pace, making this an ideal time for visitors who prefer a more authentic, unhurried experience of everyday city life rather than large crowds drawn in by a single major headline event.

What to Pack for Chicago in September

Based on 13°C average highs and 4 rainy days

Warm jacket (down or fleece)
Merino wool base layer (regulates temperature and resists odour)
Sweaters and lined trousers
Scarf and lightweight gloves
Comfortable walking shoes (a second pair lets the first air out overnight)
Universal travel adapter
Small day pack for city exploration
Reusable water bottle

Best Activities in Chicago in September

Explore the old town's cobblestone backstreetsMorning (9-11am)At 13°C, conditions are pleasant for unhurried exploration on foot
Visit hilltop viewpoints for panoramic city viewsLate afternoon (4-6pm)Low sun angle creates dramatic light for photography while temperatures remain comfortable
Bicycle rental for a half-day city circuitMid-morning startMild 13°C temperatures are ideal for extended cycling without excessive effort
Boat tour of the river, bay, or canal networkLate morning departureComfortable weather makes open-deck boats viable without wind-chill concerns
Afternoon in a world-class museum or galleryAfternoon (2-5pm)Pairs well with outdoor morning activities and provides a mid-day rest from sightseeing
Coffee-house or traditional cafe culture experienceMid-morning or post-lunchA cultural ritual in this region that rewards slow appreciation regardless of weather
Evening live music, theatre, or opera performanceEvening shows typically at 7-9pmConsistent evening temperatures make getting to and from evening venues comfortable
Visit the main botanical garden or city park at seasonal peakYear-round; best light in morningSeptember brings distinct seasonal changes to public green spaces worth exploring
Warm up with traditional hot dishes: local stew, fondue, or braised specialities at a neighbourhood restaurantLunch (12-2pm) or dinner (7-9pm)Cold-weather cuisine is a genuine cultural experience and the best local restaurants serve their heartiest dishes in cooler months

Why is Chicago cool in September?

September brings the first meaningful shift toward cooler conditions in Chicago, as the sun angle drops and day length shortens. Temperatures averaging 13°C by day and 1°C overnight are still comfortable by most standards, but the trend is clearly downward. At 42 degrees north latitude, autumn light has a particular quality: lower in the sky and warmer in tone, it gives the city a photogenic quality quite different from summer. Evening temperatures already demand a jacket, but midday hours stay pleasant for sightseeing. Climate data: Open-Meteo ERA5 (1991–2020).

Sunshine Hours

The average number of hours per day with direct sunlight. Calculated from satellite measurements. Days with more than 7 hours of sunshine are ideal for outdoor activities. Under 3 hours means overcast conditions dominate.

UV Index

A scale from 0-11+ measuring ultraviolet radiation intensity. UV 0-2: Minimal risk. UV 3-5: Moderate -- wear sunscreen. UV 6-7: High -- hat and SPF 30+ essential. UV 8-10: Very High -- limit midday exposure. UV 11+: Extreme -- seek shade between 10am-4pm.

Rain Days

A rain day is counted when precipitation exceeds 0.1mm. This threshold captures even light drizzle. Unlike total rainfall in mm, rain days tells you how often you might need an umbrella, which is useful for planning outdoor activities.

Humidity

Relative humidity as a percentage. Below 40%: Dry -- skin and throat may feel parched. 40-60%: Comfortable -- ideal for most people. 60-80%: Sticky -- light, breathable fabrics recommended. Above 80%: Muggy -- heat feels more intense; quick-dry clothing is essential.

Frequently Asked Questions: Chicago in September

In September, Chicago experiences average highs of 13°C (55°F) and lows of 1°C (34°F). Expect around 4 rainy days and 4 hours of sunshine per day, with humidity averaging 65%. The 12°C gap between daytime and overnight temperatures is worth planning around: light layers work for most visitors during the day, but an extra jacket is essential for evenings. UV index averages 6, so sun protection is advisable on clear days.

Chicago typically sees 4 rainy days in September, with total precipitation of around 50mm. This makes September one of the drier months of the year, and a reliable window for outdoor sightseeing and day trips. Rain showers tend to be brief when they do occur. For context, the driest month in Chicago typically sees 4-6 fewer rain days than September.

Pack a warm jacket, sweaters, and layering pieces for Chicago in September. Temperatures can drop to 1°C at night, so thermal underlayers are advisable for evening outings. Waterproof footwear is a sensible precaution even though rain days are limited. A scarf, hat, and gloves handle the windchill on clear cold days, which often feel colder than the thermometer reads.

September is a reasonable time to visit Chicago. Expect 4 rainy days, so pack a light rain layer for flexibility. Average temperatures of 13°C make outdoor exploration comfortable during the dry periods. With 4 daily sunshine hours, there are reliable windows of good weather to plan outdoor activities around, even if the month is not the driest on the calendar.

The average high temperature in Chicago in September is 13°C (55°F), and the average low is 1°C (34°F). The mean daily temperature is approximately 7°C (45°F). The day-to-night range of 12°C is moderate, meaning a single light jacket covers most situations. These are 30-year climate normals based on the 1991 to 2020 reference period; individual years will vary, particularly in transitional months like spring and autumn.

The best month to visit Chicago is generally May. May offers the most sunshine at 7 hours per day and only 6 rainy days. Average temperatures reach 22°C, making it comfortable for sightseeing, outdoor dining, and exploring the city. If your travel dates are flexible, planning your trip around May gives you the best chance of dry, bright weather.

September is shoulder or low season in Chicago, meaning fewer tourists and generally lower prices than peak months. With 4 sunshine hours and 4 rainy days, the weather is less of a draw for mass tourism. This is an advantage for travellers who prefer a quieter, more relaxed experience with shorter queues and easier accommodation availability.

In September, Chicago suits a range of activities thanks to cool conditions around 13°C. With few rainy days, outdoor activities are highly recommended. Top options include exploring historic neighbourhoods, visiting museums and galleries, local food markets, and day trips to surrounding areas. Cosy cafes and cultural venues make ideal retreats on overcast days.

September ranks 7th sunniest of the year in Chicago, with an average 4 daily sunshine hours. The driest months are January, February, and October. June is the hottest month (24°C avg high); December is the coolest (3°C). From here, temperatures fall 5°C into October. Compared to last month (August: 19°C high, 5 rain days), September is cooler and drier. September sits in the middle of the annual sunshine ranking for Chicago, offering a reasonable balance of good weather and manageable crowds.

Year-Round Climate

Month	High	Low	Rain Days	Sun	Details
January	4°C	-8°C	3	1h	View
February	8°C	-4°C	3	3h	View
March	13°C	1°C	4	4h	View
April	19°C	7°C	5	6h	View
May	22°C	10°C	6	7h	View
June	24°C	12°C	6	7h	View
July	22°C	10°C	6	7h	View
August	19°C	7°C	5	6h	View
September	13°C	1°C	4	4h	View
October	8°C	-4°C	3	3h	View
November	4°C	-8°C	3	1h	View
December	3°C	-9°C	3	1h	View

Other Months in Chicago

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Plan Your Trip to Chicago

Best Time to Visit Chicago

Data Sources for Chicago

Chicago on Wikipedia Open-Meteo Climate API NOAA National Centers UK Met Office WMO GeoNames

Climate normals represent 30-year averages (1991-2020). Individual years may vary.