August 21 is generally a great time to visit Chicago. While there is a slight chance of rain (24%), showers are usually brief. Expect comfortable 25°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 August 21
"Warm & Sunny. Expect average highs of 25.3°C. 24% chance of rain."
What to Wear in Chicago in August
Based on historical data for August 21, Chicago typically experiences temperatures between 19°C and 25.3°C. We recommend packing t-shirt, light clothing to stay comfortable. Trends suggest it will stay mostly dry (24% rain probability), but checking the forecast before heading out is always wise.
Complete Packing Guide
Weekly breakdown & essential items for Chicago
Smart Suitcase
- T-Shirt
- Light Clothing
Average High
25.3°C
Daytime Peak
Average Low
19°C
Nighttime Low
Feels Like
26.2°C
☀️ Feels accurate
Rain Chance
24%
Avg 2.2mm if it rains
Cloud Cover
49%
Overcast
Pressure
1016.2 hPa
Low volatility
Chicago Weather Conditions & UV Index
Weather Confidence
30-year variance analysis
Based on 10 years of data
🎯 This date historically delivers consistent weather 83% of the time. Safe to plan outdoor activities with confidence.
Sun Exposure
UV Index & Safety Guide
Protection Needed
SPF 30 recommended
05:00 - 10:00
16:00 - 18:00
Type I-II
🔴 18 min to burn
Type III-IV
🟡 27 min to burn
Type V-VI
🟢 45 min to burn
UV estimate based on latitude, season & cloud cover. Actual UV may vary.
Outdoor Comfort
How pleasant is it outside?
Dew Point
20.3°C
Humid/Sticky
Heat Stress
Low
No heat warning
🙂 Best outdoor time:
Morning hours (before 11 AM)
Travel & Logistics Insights
Local Calendar
Business Day
Standard hours in United States
Flight Traffic
High
97/100 pressure index
Health Advisory
Healthy
Routine only • View Details →
Landing Slots
~1,331
Daily arrival options (inc. codeshare)
Sunrise, Sunset & Wind in Chicago
Daylight & Sun
Solar Elevation Cycle
🌅 Sunrise
05:06
☀️ Noon
11:55
🌇 Sunset
18:44
⏱️ Daylight
13h 37m
Wind Speed
19 km/h
Gentle breeze
Sunshine
11.0 hrs
Direct Sun (Cloud-free)
Humidity
74%
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
☀️ Excellent
Tourist Crowds
🔴 Very Busy
Price Level
💰💰💰 Expensive
Health & Wellbeing
Meteo-Health Forecast
Stable conditions. Low risk of headaches.
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 August 21 averages 25.3°C with a 24% 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
August 14
25.6°C • 21% rain
Score
97
August 15
25.6°C • 21% rain
Score
97
August 28
25.8°C • 22% rain
Score
96
💡 Moving your event by a few days could significantly improve weather conditions
Compare Other Cities
Same date (August 21) in other destinations
🌍 Explore the same date in different destinations around the world
📍 Is Chicago Worth Visiting on August 21?
Planning a trip to Chicago on August 21? Our historical weather analysis based on 30 years of NASA satellite data shows that this time of year typically offers vibrant summer conditions averaging 25.3°C with a 24% historical precipitation risk.
✈️ Travel Logistics: Approximately 1,331 landing slots available daily during this period, indicating peak tourist activity.
📊 Historical Extremes: The hottest August 21 recorded in the last 30 years saw temperatures hit 30.4°C in 2021, while the coldest dropped to 13.2°C in 2024.