Baltimore Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Baltimore (Baltimore-Columbia-Towson, MD area) was June 29, 2023, when the daily AQI reached 205 (Very Unhealthy), set by ground-level ozone, in peak ozone season. Across 2,556 monitored days in 2019–2025, 5 of the 10 worst days were Unhealthy (AQI 151+) or worse; 8 of the 10 were driven by ground-level ozone and 2 by fine particulate matter (PM2.5), and 4 of them fell in 2023. The cleanest day was January 10, 2024 at AQI 14 (Good); the 10 best days span 5 different years.
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When were Baltimore's worst and best air quality days?
Worst: June 29, 2023, AQI 205 (Very Unhealthy, O3). Best: January 10, 2024, AQI 14 (Good). Based on 2,556 EPA-monitored days in the Baltimore-Columbia-Towson, MD area, 2019–2025.
- ✓5 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 136 (Unhealthy for Sensitive Groups).
- ✓Ground-level ozone drove 8 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 Baltimore?▾
June 29, 2023: the Baltimore-Columbia-Towson, MD area's daily AQI hit 205 (Very Unhealthy), driven by ground-level ozone, in peak ozone season. That is the highest of 2,556 monitored days in 2019–2025.
What was the best air quality day in Baltimore?▾
January 10, 2024, with a daily AQI of 14 (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 Baltimore's worst air quality day in 2025?▾
June 12, 2025, AQI 143 (Unhealthy for Sensitive Groups), set by ground-level ozone, in peak ozone season.
Which pollutant causes Baltimore's worst air days?▾
Ground-level ozone set the AQI on 8 of the 10 worst days; fine particulate matter (PM2.5) on 2. The tables above list the defining pollutant for every day.
Baltimore's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Baltimore-Columbia-Towson, MD 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) | 205 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 2 | (2023 page) | 200 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 170 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2024 page) | 154 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 5 | (2023 page) | 154 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 6 | (2019 page) | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 7 | (2025 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 8 | (2019 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 9 | (2021 page) | 140 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 10 | (2025 page) | 136 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Baltimore
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 | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 119 | 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 | 122 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 205 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2024 | 154 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Baltimore's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Baltimore-Columbia-Towson, MD area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2024 page) | 14 | Good | NO2 — nitrogen dioxide |
| 2 | (2023 page) | 19 | Good | O3 — ground-level ozone |
| 3 | (2020 page) | 19 | Good | O3 — ground-level ozone |
| 4 | (2023 page) | 20 | Good | O3 — ground-level ozone |
| 5 | (2024 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2022 page) | 21 | Good | O3 — ground-level ozone |
| 7 | (2021 page) | 21 | Good | O3 — ground-level ozone |
| 8 | (2020 page) | 21 | Good | O3 — ground-level ozone |
| 9 | (2024 page) | 22 | Good | O3 — ground-level ozone |
| 10 | (2023 page) | 22 | Good | O3 — ground-level ozone |
Right now in Baltimore
The latest EPA AirNow observation puts Baltimore's AQI at 43 (PM2.5). The days above are historical records, not today's reading.
View current Baltimore air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Baltimore-Columbia-Towson, MD), 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.