Houston Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Houston (Houston-The Woodlands-Sugar Land, TX area) was May 18, 2023, when the daily AQI reached 205 (Very Unhealthy), set by ground-level ozone. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 9 of the 10 were driven by ground-level ozone and 1 by fine particulate matter (PM2.5), and 5 of them fell in 2024. The cleanest day was September 24, 2020 at AQI 22 (Good); the 10 best days span 5 different years.
Extra Protection for Houston Homes
Air quality in Houston is moderate (AQI 57), 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 Houston's worst and best air quality days?
Worst: May 18, 2023, AQI 205 (Very Unhealthy, O3). Best: September 24, 2020, AQI 22 (Good). Based on 2,557 EPA-monitored days in the Houston-The Woodlands-Sugar Land, TX area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 185 (Unhealthy).
- ✓Ground-level ozone drove 9 of the 10 worst days.
- ✓2024 accounts for 5 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Houston?▾
May 18, 2023: the Houston-The Woodlands-Sugar Land, TX area's daily AQI hit 205 (Very Unhealthy), driven by ground-level ozone. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Houston?▾
September 24, 2020, with a daily AQI of 22 (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 Houston's worst air quality day in 2025?▾
March 1, 2025, AQI 179 (Unhealthy), set by ground-level ozone.
Which pollutant causes Houston's worst air days?▾
Ground-level ozone set the AQI on 9 of the 10 worst days; fine particulate matter (PM2.5) on 1. The tables above list the defining pollutant for every day.
Houston's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Houston-The Woodlands-Sugar Land, 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) | 205 | Very Unhealthy | O3 — ground-level ozone |
| 2 | (2019 page) | 202 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 3 | (2024 page) | 201 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 4 | (2024 page) | 200 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 5 | (2023 page) | 197 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 6 | (2024 page) | 192 | Unhealthy | O3 — ground-level ozone |
| 7 | (2020 page) | 190 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2023 page) | 187 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 9 | (2024 page) | 185 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 10 | (2024 page) | 185 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Houston
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 | 202 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 190 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2021 | 179 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2022 | 179 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 205 | Very Unhealthy | O3 — ground-level ozone | |
| 2024 | 201 | Very Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 179 | Unhealthy | O3 — ground-level ozone |
Houston's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Houston-The Woodlands-Sugar Land, TX area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2019 page) | 22 | Good | O3 — ground-level ozone |
| 3 | (2020 page) | 23 | Good | O3 — ground-level ozone |
| 4 | (2023 page) | 24 | Good | O3 — ground-level ozone |
| 5 | (2022 page) | 24 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2020 page) | 24 | Good | O3 — ground-level ozone |
| 7 | (2023 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2024 page) | 27 | Good | O3 — ground-level ozone, in peak ozone season |
| 9 | (2022 page) | 27 | Good | O3 — ground-level ozone |
| 10 | (2024 page) | 28 | Good | O3 — ground-level ozone |
Right now in Houston
The latest EPA AirNow observation puts Houston's AQI at 57 (PM2.5). The days above are historical records, not today's reading.
View current Houston air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Houston-The Woodlands-Sugar Land, 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.