Bad Air Days in Seminole County, Florida: under 1 a Year
under 1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 746 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly ozone: summer smog (29% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in January and May and March and April and October. Averaged over 2016 to 2025.
What actually helps here
- Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
- On the odd bad day, check AirNow and keep windows shut.
Better or worse than it was
In 2000 to 2009 this county averaged 8 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2017, with 2 bad days on 355 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2018-04-18 | 150 | Ozone |
| 2024-01-01 | 149 | PM2.5 |
| 2017-05-10 | 133 | Ozone |
| 2018-03-24 | 119 | Ozone |
| 2017-05-11 | 112 | Ozone |
Most days, not the worst ones
Across 3,556 monitored days from 2016 to 2025, the air in Seminole County rated Good on 82% of them, more often than the 72% typical of monitored counties, and Moderate on 18%. The median day sat at AQI 40; one day in ten went above 55.
The pollutant setting the AQI on an ordinary day here:
- ozone58%2,056 days
- fine particles (PM2.5)42%1,481 days
- coarse dust (PM10)1%19 days
Seminole County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 363 | 307 | 56 | 0 | 0 | 39 | 97 |
| 2024 | 286 | 204 | 81 | 1 | 0 | 43 | 149 |
| 2023 | 364 | 299 | 64 | 1 | 0 | 40 | 106 |
| 2022 | 363 | 288 | 75 | 0 | 0 | 42 | 87 |
| 2021 | 365 | 273 | 92 | 0 | 0 | 42 | 97 |
| 2020 | 365 | 287 | 78 | 0 | 0 | 40 | 84 |
| 2019 | 365 | 296 | 68 | 1 | 0 | 39 | 110 |
| 2018 | 365 | 309 | 54 | 2 | 0 | 39 | 150 |
| 2017 | 355 | 311 | 42 | 2 | 0 | 38 | 133 |
| 2016 | 365 | 325 | 40 | 0 | 0 | 38 | 87 |
| 2015 | 361 | 334 | 27 | 0 | 0 | 35 | 80 |
| 2014 | 364 | 326 | 38 | 0 | 0 | 36 | 97 |
| 2013 | 365 | 330 | 35 | 0 | 0 | 35 | 93 |
| 2012 | 359 | 311 | 44 | 4 | 0 | 37 | 112 |
| 2011 | 364 | 316 | 44 | 4 | 0 | 39 | 136 |
| 2010 | 364 | 290 | 71 | 3 | 0 | 39 | 105 |
*2025 may be a partial year in EPA's file.
Florida compared
- Hillsborough County3/yr
- Miami-Dade County3/yr
- Duval County2/yr
- Broward County1/yr
- Osceola County1/yr
- Orange Countyunder 1/yr
- Polk Countyunder 1/yr
- Pinellas Countyunder 1/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.