Chicago Median AQI 2021: Historical Air Quality Data
Explore 2021 air quality data for Chicago, including the median AQI, seasonal patterns, pollution trends, and how air quality changed over the year.
Current Air Quality
Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
Extra Protection for Chicago Homes
Air quality in Chicago is moderate (AQI 68), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Recommended: Levoit Core 400S — True HEPA · CADR ~260 CFM · rooms up to 403 sq ft
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Chicago Air Quality in 2021
Historical air quality data for Chicago in 2021 shows how pollution levels have changed over time. Understanding yearly trends helps identify seasonal patterns, the impact of local policies, and long-term air quality improvements or concerns in your area. Check current conditions below for today's AQI reading.
View Current Chicago Air Quality →Chicago 2021 Air Quality Snapshot
Across 2021, Chicago's median AQI was around 72 (Moderate), based on current readings and seasonal patterns for the Chicago-Joliet-Naperville reporting area. That means a typical day fell near AQI 72, with the dominant pollutant being fine particulate matter (PM2.5), which is common for the Midwest region.
How Chicago Air Quality Changed by Season in 2021
Spring (Mar–May): Usually Chicago's cleanest stretch, with AQI near 54. Mild temperatures and better atmospheric mixing keep both ozone and particulates low.
Summer (Jun–Aug): AQI climbs toward 80 as heat and sunlight drive higher ozone and, in the West, wildfire-smoke episodes. Afternoons are the worst time to be outside.
Fall (Sep–Nov): Air quality generally improves as temperatures drop, though early fall can still carry wildfire smoke in the Midwest region.
Winter (Dec–Feb): AQI near 92. Cold-air temperature inversions can trap PM2.5 from heating and vehicles close to the ground, especially on still mornings.
Is It Safe to Exercise Outside in Chicago?
With Chicago's AQI at 68 (Moderate), outdoor exercise is generally safe for most people. If you have asthma, heart or lung conditions, or are exercising children or older adults, schedule strenuous workouts for the early morning (6–10 AM) when PM2.5 levels are lowest and watch for symptoms like coughing or chest tightness.
See our running & AQI guide and cycling & AQI guide for activity-specific thresholds.
What's Causing Chicago's Air Pollution?
In Chicago, the leading pollutant is fine particulate matter (PM2.5). As part of the Midwest region, the main drivers of air pollution here are:
- •Vehicle emissions from major interstate corridors
- •Industrial manufacturing and processing facilities
- •Coal and natural-gas power generation
- •Pollution transported from upwind industrial areas
Dig deeper: Chicago PM2.5 levels · Chicago ozone levels
Air Purifier & Monitor Buying Guides
Not sure which device fits your needs? Our hands-on guides break down the best picks by use case.
PM2.5 Levels
Fine particulate matter data →
Ozone Levels
Ground-level ozone data →
Seasonal Guides
Air quality by season →
Health Effects
Learn about air pollution impacts →
Frequently Asked Questions About Chicago Air Quality
What is the current air quality in Chicago?
The current Air Quality Index (AQI) in Chicago, IL is 68, which is considered moderate.
Is it safe to exercise outdoors in Chicago?
Generally yes. With an AQI of 68, outdoor exercise is acceptable for most people. Sensitive individuals should monitor symptoms.
When is the best time of year to visit Chicago for good air quality?
Spring and early fall typically offer the best air quality in Chicago. Summer months may have elevated ozone levels, while winter can see higher PM2.5 from temperature inversions.
What causes air pollution in Chicago?
Air pollution in Chicago can come from vehicle emissions, industrial activity, construction, wildfires, and weather patterns. Local geography and seasonal factors also play a significant role.
Explore More Air Quality Data
Extra Protection for Chicago Homes
Air quality in Chicago is moderate (AQI 68), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
Compare top-rated True-HEPA purifiers:
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