Aurora Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Aurora (Chicago-Naperville-Elgin, IL-IN-WI area) was June 28, 2023, when the daily AQI reached 246 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 6 of the 10 were driven by fine particulate matter (PM2.5) and 4 by ground-level ozone, and 4 of them fell in 2023. The cleanest day was October 22, 2025 at AQI 20 (Good); the 10 best days span 5 different years.
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When were Aurora's worst and best air quality days?
Worst: June 28, 2023, AQI 246 (Very Unhealthy, PM2.5). Best: October 22, 2025, AQI 20 (Good). Based on 2,557 EPA-monitored days in the Chicago-Naperville-Elgin, IL-IN-WI area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 168 (Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 6 of the 10 worst days.
- ✓2023 accounts for 4 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Aurora?▾
June 28, 2023: the Chicago-Naperville-Elgin, IL-IN-WI area's daily AQI hit 246 (Very Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Aurora?▾
October 22, 2025, with a daily AQI of 20 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Aurora's worst air quality day in 2025?▾
April 22, 2025, AQI 219 (Very Unhealthy), set by fine particulate matter (PM2.5).
Which pollutant causes Aurora's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 6 of the 10 worst days; ground-level ozone on 4. The tables above list the defining pollutant for every day.
Aurora's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Chicago-Naperville-Elgin, IL-IN-WI area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 246 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 234 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2025 page) | 219 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2022 page) | 202 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2020 page) | 197 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 6 | (2023 page) | 192 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 7 | (2021 page) | 175 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2023 page) | 174 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 9 | (2019 page) | 174 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 10 | (2025 page) | 168 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Aurora
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 174 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 197 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 175 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2022 | 202 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2023 | 246 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 166 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 219 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
Aurora's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Chicago-Naperville-Elgin, IL-IN-WI area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2025 page) | 20 | Good | O3 — ground-level ozone |
| 2 | (2021 page) | 24 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2025 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2025 page) | 27 | Good | O3 — ground-level ozone |
| 5 | (2024 page) | 28 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2023 page) | 29 | Good | O3 — ground-level ozone |
| 7 | (2022 page) | 29 | Good | O3 — ground-level ozone |
| 8 | (2025 page) | 30 | Good | O3 — ground-level ozone |
| 9 | (2025 page) | 30 | Good | O3 — ground-level ozone |
| 10 | (2024 page) | 30 | Good | O3 — ground-level ozone |
Right now in Aurora
The latest EPA AirNow observation puts Aurora's AQI at 39 (PM2.5). The days above are historical records, not today's reading.
View current Aurora 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.