Chicago Air Quality in Spring
Across 2019–2025, Chicago's spring (March–May) air quality had a median AQI of 55 (Moderate) over 644 monitored days in the Chicago-Naperville-Elgin, IL-IN-WI area. 2.7% of spring days (17 of 644) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 66.1% of days. The cleanest spring on record here was 2019 (median AQI 58, 0 days above 100) and the worst was 2023 (median 61, 8 days above 100, peak AQI 143).
- Good: 30.4%
- Moderate: 66.9%
- Unhealthy for Sensitive Groups: 2.2%
- Unhealthy or worse: 0.5%
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How is the air in Chicago in spring?
Moderate on a typical day: median AQI 55 across 2019–2025, with 2.7% of spring days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓30.4% of spring days were Good (AQI 0–50), 66.9% Moderate (51–100).
- ✓17 days of 644 reached AQI 101+; the spring peak was 219.
- ✓Cleanest month: March; worst month: May.
Frequently asked questions
What is the air quality like in Chicago in spring?▾
Across 2019–2025, the median daily AQI in Chicago in spring was 55 (Moderate). 30.4% of days were Good, 66.9% Moderate, and 2.7% reached Unhealthy for Sensitive Groups or worse, based on 644 monitored days in EPA's Air Quality System.
Is spring a good time for outdoor exercise in Chicago?▾
A typical spring 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 37 of spring days (2.7%) 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 spring air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 66.1% of spring days in Chicago. The highest spring AQI recorded in 2019–2025 was 219 (Very Unhealthy), in 2023.
Chicago spring air quality, year by year
Chicago spring 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 |
|---|---|---|---|---|---|
| 2019cleanest | 92 | 58 | 0 | 97 | PM2.5 |
| 2020 | 92 | 59 | 0 | 96 | PM2.5 |
| 2021 | 92 | 59 | 3 | 175 | PM2.5 |
| 2022 | 92 | 53 | 2 | 108 | PM2.5 |
| 2023worst | 92 | 61 | 8 | 143 | PM2.5 |
| 2024 | 92 | 54 | 1 | 166 | PM2.5 |
| 2025 | 92 | 52 | 3 | 219 | PM2.5 |
What spring air means in Chicago
A typical spring 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 37 of spring days (2.7%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Spring'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 Spring AQI across every EPA metro area (307,196 metro-days, 2019–2025) is 43, so Chicago runs above the national Spring norm; 2.7% of its Spring days topped AQI 100 versus 0.8% nationally (above average).
Within the season, March is the cleanest month (median AQI 55, 1.0% of days above 100) and May the worst (median 58, 4.6% above 100).
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 season 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.