Chicago Air Quality in March
Across 2019–2025, Chicago's March air quality had a median AQI of 55 (Moderate) over 217 monitored days in the Chicago-Naperville-Elgin, IL-IN-WI area. 1.0% of March days (2 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 76.5% of days. The cleanest March on record here was 2022 (median AQI 52, 0 days above 100) and the worst was 2024 (median 53, 1 day above 100, peak AQI 166).
- Good: 27.6%
- Moderate: 71.4%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.5%
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How is the air in Chicago in March?
Moderate on a typical day: median AQI 55 across 2019–2025, with 1.0% of March days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓27.6% of March days were Good (AQI 0–50), 71.4% Moderate (51–100).
- ✓2 days of 217 reached AQI 101+; the March peak was 166.
- ✓Best March: 2022; worst March: 2024.
Frequently asked questions
What is the air quality like in Chicago in March?▾
Across 2019–2025, the median daily AQI in Chicago in March was 55 (Moderate). 27.6% of days were Good, 71.4% Moderate, and 1.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is March a good time for outdoor exercise in Chicago?▾
A typical March day in Chicago is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 100 of March days (1.0%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Chicago's March air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 76.5% of March days in Chicago. The highest March AQI recorded in 2019–2025 was 166 (Unhealthy), in 2024.
Chicago March air quality, year by year
Chicago March air quality by year (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 60 | 0 | 97 | PM2.5 |
| 2020 | 31 | 57 | 0 | 96 | PM2.5 |
| 2021 | 31 | 61 | 0 | 83 | PM2.5 |
| 2022cleanest | 31 | 52 | 0 | 85 | PM2.5 |
| 2023 | 31 | 54 | 0 | 82 | PM2.5 |
| 2024worst | 31 | 53 | 1 | 166 | PM2.5 |
| 2025 | 31 | 50 | 1 | 137 | PM2.5 |
What March air means in Chicago
A typical March day in Chicago is Moderate (median AQI 55): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 100 of March days (1.0%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
March's median AQI of 55 is below Chicago's whole-year median of 60, making it one of the area's cleaner periods. Nationally, the median March AQI across every EPA metro area (102,455 metro-days, 2019–2025) is 42, so Chicago runs above the national March norm; 1.0% of its March days topped AQI 100 versus 0.4% nationally (about the same).
March is part of Chicago's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Chicago
The latest EPA AirNow observation puts Chicago's AQI at 46 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Chicago air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Chicago-Naperville-Elgin, IL-IN-WI), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.