September 21 is generally a great time to visit Chicago. While there is a slight chance of rain (29%), showers are usually brief. Expect comfortable 22°C weather. Chicago is currently in its most popular travel window, meaning vibrant crowds and premium pricing.
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Essential Travel Info for Chicago
Currency
USD
$ United States dollar
Language
English
Driving
Right side
Connect
The first Internet café in the United St...
Safety
Moderate Safety
GPI: 2.44
Chicago Weather Forecast for September 21
"Mild & Comfortable. Expect average highs of 22.4°C. 29% chance of rain."
What to Wear in Chicago in September
Based on historical data for September 21, Chicago typically experiences temperatures between 15.6°C and 22.4°C. We recommend packing t-shirt, light clothing to stay comfortable. With a 29% chance of rain, keeping a raincoat or umbrella handy is a smart move.
Complete Packing Guide
Weekly breakdown & essential items for Chicago
Smart Suitcase
- T-Shirt
- Light Clothing
Average High
22.4°C
Daytime Peak
Average Low
15.6°C
Nighttime Low
Feels Like
22.8°C
☀️ Feels accurate
Rain Chance
29%
Avg 1.9mm if it rains
Cloud Cover
52%
Overcast
Pressure
1016.6 hPa
Medium volatility
Chicago Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
🎯 This date historically delivers consistent weather 93% of the time. Safe to plan outdoor activities with confidence.
Sun Exposure
UV Index & Safety Guide
Protection Needed
SPF 15 for extended outdoor time
Type I-II
🔴 28 min to burn
Type III-IV
🟡 42 min to burn
Type V-VI
🟢 70 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
17.1°C
Noticeable
Heat Stress
Low
No heat warning
😊 Best outdoor time:
Any time during daylight hours
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in United States
Flight Traffic
High
96/100 pressure index
Health Advisory
Healthy
Routine only • View Details →
Landing Slots
~1,314
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in Chicago
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
05:38
☀️ Noon
11:44
🌇 Sunset
17:51
⏱️ Daylight
12h 13m
Wind Speed
21.1 km/h
Moderate wind
Sunshine
8.9 hrs
Direct Sun (Cloud-free)
Humidity
72%
Humid / Damp
Travel Intelligence
Exclusive flight analytics & health data for Chicago
Smart Flight Estimator
Airport-to-Airport Logistics
unlock smart flight estimates
Add your home location in settings to see airport details.
Travel Health & Safety in Chicago
Travel Comfort Index
Real-time tourism conditions
Weather Quality
⛅ Good
Tourist Crowds
🟡 Busy
Price Level
💰💰💰 Expensive
Health & Wellbeing
Meteo-Health Forecast
Moderate fluctuations. Some sensitivity possible.
Weather unlikely to affect joint pain.
Moderate fish activity expected.
Air quality is acceptable. Sensitive individuals should limit prolonged outdoor exertion.
Regional Safety Profile
Seismic Activity
Zero seismic activity detected in 30 years.
"According to 30YearWeather's analysis of 30 years of NASA satellite data, Chicago on September 21 averages 22.4°C with a 29% precipitation probability. Wedding/Outdoor Event Score: 95/100."
— Source: 30YearWeather.com|Data: NASA POWER (1991-2021)|View Methodology
Chicago Weather History (2010–2024)
Temperature History
Hall of Fame
Records from last 10 years
Better Alternatives Nearby
Consider these dates within ±7 days
September 14
23.1°C • 17% rain
Score
99
September 15
23.2°C • 18% rain
Score
99
September 16
23.1°C • 16% rain
Score
99
💡 Moving your event by a few days could significantly improve weather conditions
Compare Other Cities
Same date (September 21) in other destinations
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Czech Republic
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Rome
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London
United Kingdom
Amsterdam
Netherlands
🌍 Explore the same date in different destinations around the world
📍 Is Chicago Worth Visiting on September 21?
Planning a trip to Chicago on September 21? Our historical weather analysis based on 30 years of NASA satellite data shows that this time of year is characterized by pleasant mild weather averaging 22.4°C with a 29% historical precipitation risk.
✈️ Travel Logistics: Approximately 1,314 landing slots available daily during this period, indicating peak tourist activity.
📊 Historical Extremes: The hottest September 21 recorded in the last 30 years saw temperatures hit 31.6°C in 2017, while the coldest dropped to 11.1°C in 2020.