San Antonio Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for San Antonio (San Antonio-New Braunfels, TX area) was January 1, 2023, when the daily AQI reached 309 (Hazardous), set by fine particulate matter (PM2.5). Across 2,557 monitored days in 2019–2025, 8 of the 10 worst days were Unhealthy (AQI 151+) or worse; 7 of the 10 were driven by fine particulate matter (PM2.5) and 3 by ground-level ozone, and 3 of them fell in 2024. The cleanest day was October 27, 2020 at AQI 15 (Good); the 10 best days span 5 different years.
Extra Protection for San Antonio Homes
Air quality in San Antonio is moderate (AQI 52), 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 San Antonio's worst and best air quality days?
Worst: January 1, 2023, AQI 309 (Hazardous, PM2.5). Best: October 27, 2020, AQI 15 (Good). Based on 2,557 EPA-monitored days in the San Antonio-New Braunfels, TX 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).
- ✓Fine particulate matter (PM2.5) drove 7 of the 10 worst days.
- ✓2024 accounts for 3 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in San Antonio?▾
January 1, 2023: the San Antonio-New Braunfels, TX area's daily AQI hit 309 (Hazardous), driven by fine particulate matter (PM2.5). That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in San Antonio?▾
October 27, 2020, with a daily AQI of 15 (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 San Antonio's worst air quality day in 2025?▾
September 10, 2025, AQI 154 (Unhealthy), set by ground-level ozone.
Which pollutant causes San Antonio's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 7 of the 10 worst days; ground-level ozone on 3. The tables above list the defining pollutant for every day.
San Antonio's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the San Antonio-New Braunfels, TX 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) | 309 | Hazardous | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2022 page) | 214 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2024 page) | 199 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2019 page) | 175 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2023 page) | 166 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2020 page) | 160 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2025 page) | 154 | Unhealthy | O3 — ground-level ozone |
| 8 | (2024 page) | 152 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2024 page) | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
| 10 | (2021 page) | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
Worst day of each year in San Antonio
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 | 175 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2020 | 160 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone | |
| 2022 | 214 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2023 | 309 | Hazardous | PM2.5 — fine particulate matter (PM2.5) | |
| 2024 | 199 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2025 | 154 | Unhealthy | O3 — ground-level ozone |
San Antonio's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the San Antonio-New Braunfels, TX area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 15 | Good | O3 — ground-level ozone |
| 2 | (2019 page) | 19 | Good | O3 — ground-level ozone |
| 3 | (2025 page) | 22 | Good | O3 — ground-level ozone |
| 4 | (2020 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2020 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2024 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2020 page) | 23 | Good | O3 — ground-level ozone |
| 8 | (2020 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2024 page) | 24 | Good | O3 — ground-level ozone |
| 10 | (2023 page) | 24 | Good | O3 — ground-level ozone |
Right now in San Antonio
The latest EPA AirNow observation puts San Antonio's AQI at 52 (PM2.5). The days above are historical records, not today's reading.
View current San Antonio air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Antonio-New Braunfels, TX), 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.