Bad Air Days in Brazoria County, Texas: 8 a Year
8 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 127 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (0% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in September and October and August and June. Averaged over 2016 to 2025.
What to buy, and what not to
- Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.
The record for Brazoria
In 2000 to 2009 this county averaged 26 bad days a year; in 2016 to 2025, 8. The air has improved. The worst recent year was 2023, with 17 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2020-08-18 | 182 | Ozone |
| 2018-07-26 | 166 | Ozone |
| 2024-06-06 | 164 | Ozone |
| 2019-06-12 | 161 | Ozone |
| 2021-09-08 | 159 | Ozone |
An ordinary day in Brazoria
Across 3,643 monitored days from 2016 to 2025, the air in Brazoria County rated Good on 86% of them, more often than the 72% typical of monitored counties, and Moderate on 12%. The median day sat at AQI 35; one day in ten went above 59.
The pollutant setting the AQI on an ordinary day here:
- ozone96%3,487 days
- fine particles (PM2.5)2%81 days
- nitrogen dioxide2%75 days
Brazoria County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 295 | 62 | 8 | 0 | 35 | 143 |
| 2024 | 365 | 303 | 56 | 6 | 1 | 37 | 164 |
| 2023 | 365 | 301 | 47 | 17 | 1 | 36 | 156 |
| 2022 | 365 | 311 | 46 | 8 | 0 | 35 | 119 |
| 2021 | 365 | 331 | 22 | 12 | 1 | 34 | 159 |
| 2020 | 365 | 328 | 34 | 3 | 1 | 33 | 182 |
| 2019 | 365 | 325 | 33 | 7 | 1 | 33 | 161 |
| 2018 | 365 | 329 | 31 | 5 | 1 | 31 | 166 |
| 2017 | 357 | 306 | 44 | 7 | 1 | 37 | 154 |
| 2016 | 366 | 313 | 50 | 3 | 0 | 36 | 115 |
| 2015 | 365 | 308 | 42 | 15 | 4 | 33 | 164 |
| 2014 | 365 | 330 | 31 | 4 | 1 | 32 | 174 |
| 2013 | 365 | 316 | 41 | 8 | 3 | 34 | 172 |
| 2012 | 366 | 283 | 62 | 21 | 5 | 34 | 233 |
| 2011 | 365 | 289 | 45 | 31 | 8 | 36 | 203 |
| 2010 | 365 | 304 | 40 | 21 | 6 | 36 | 172 |
*2025 may be a partial year in EPA's file.
Texas compared
- Harris County29/yr
- El Paso County26/yr
- Tarrant County19/yr
- Denton County17/yr
- Dallas County12/yr
- Collin County11/yr
- Bexar County11/yr
- Cameron County9/yr
How this is counted
A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.