Cincinnati Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Cincinnati (Cincinnati, OH-KY-IN area) was June 28, 2023, when the daily AQI reached 197 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 8 of the 10 worst days were Unhealthy (AQI 151+) or worse; 5 of the 10 were driven by ground-level ozone and 5 by fine particulate matter (PM2.5), and 5 of them fell in 2023. The cleanest day was October 16, 2023 at AQI 21 (Good); the 10 best days span 3 different years.
Extra Protection for Cincinnati Homes
Air quality in Cincinnati is moderate (AQI 65), 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: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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When were Cincinnati's worst and best air quality days?
Worst: June 28, 2023, AQI 197 (Unhealthy, PM2.5). Best: October 16, 2023, AQI 21 (Good). Based on 2,557 EPA-monitored days in the Cincinnati, OH-KY-IN area, 2019–2025.
- ✓8 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 147 (Unhealthy for Sensitive Groups).
- ✓Ground-level ozone drove 5 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 Cincinnati?▾
June 28, 2023: the Cincinnati, OH-KY-IN area's daily AQI hit 197 (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 Cincinnati?▾
October 16, 2023, with a daily AQI of 21 (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 Cincinnati's worst air quality day in 2025?▾
July 5, 2025, AQI 154 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season.
Which pollutant causes Cincinnati's worst air days?▾
Ground-level ozone set the AQI on 5 of the 10 worst days; fine particulate matter (PM2.5) on 5. The tables above list the defining pollutant for every day.
Cincinnati's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Cincinnati, OH-KY-IN 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) | 197 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 164 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 4 | (2025 page) | 154 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2023 page) | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2023 page) | 152 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2025 page) | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 8 | (2022 page) | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 9 | (2025 page) | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
| 10 | (2024 page) | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Cincinnati
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 | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 126 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 197 | 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 | 154 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Cincinnati's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Cincinnati, OH-KY-IN area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2024 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2023 page) | 23 | Good | O3 — ground-level ozone |
| 5 | (2024 page) | 25 | Good | O3 — ground-level ozone |
| 6 | (2024 page) | 25 | Good | O3 — ground-level ozone |
| 7 | (2024 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2023 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2023 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2022 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Cincinnati
The latest EPA AirNow observation puts Cincinnati's AQI at 65 (PM2.5). The days above are historical records, not today's reading.
View current Cincinnati air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Cincinnati, OH-KY-IN), 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.