Dayton Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Dayton (Dayton, OH area) was June 28, 2023, when the daily AQI reached 204 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 3 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 5 of them fell in 2023. The cleanest day was October 29, 2023 at AQI 17 (Good); the 10 best days span 4 different years.
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When were Dayton's worst and best air quality days?
Worst: June 28, 2023, AQI 204 (Very Unhealthy, PM2.5). Best: October 29, 2023, AQI 17 (Good). Based on 2,557 EPA-monitored days in the Dayton, OH area, 2019–2025.
- ✓3 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 129 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) drove 6 of the 10 worst days.
- ✓2023 accounts for 5 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Dayton?▾
June 28, 2023: the Dayton, OH area's daily AQI hit 204 (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 Dayton?▾
October 29, 2023, with a daily AQI of 17 (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 Dayton's worst air quality day in 2025?▾
July 5, 2025, AQI 129 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5), in wildfire smoke season.
Which pollutant causes Dayton'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.
Dayton's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Dayton, OH 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) | 204 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 180 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 148 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2024 page) | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 6 | (2022 page) | 136 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 7 | (2023 page) | 132 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 8 | (2025 page) | 129 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 9 | (2025 page) | 129 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 10 | (2024 page) | 129 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Dayton
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 | 95 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2020 | 112 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 101 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 136 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 204 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 129 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Dayton's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Dayton, OH area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 17 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2024 page) | 19 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2024 page) | 19 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2025 page) | 20 | Good | O3 — ground-level ozone |
| 5 | (2024 page) | 20 | Good | O3 — ground-level ozone |
| 6 | (2023 page) | 20 | Good | O3 — ground-level ozone |
| 7 | (2025 page) | 21 | Good | O3 — ground-level ozone |
| 8 | (2024 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2023 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2022 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Dayton
The latest EPA AirNow observation puts Dayton's AQI at 50 (PM2.5). The days above are historical records, not today's reading.
View current Dayton air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Dayton, OH), 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.