Bad Air Days in Sweetwater County, Wyoming: 7 a Year
7 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 157 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (60% particle days).
The bad-air season here
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and August. Averaged over 2016 to 2025.
What to buy, and what not to
- Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
- Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.
The record for Sweetwater
In 2000 to 2009 this county averaged 4 bad days a year; in 2016 to 2025, 7. It has got worse. The worst recent year was 2020, with 12 bad days on 366 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2020-05-19 | 1334 | PM10 |
| 2017-06-12 | 264 | PM10 |
| 2023-01-02 | 211 | PM10 |
| 2021-03-06 | 195 | PM10 |
| 2020-06-13 | 174 | PM10 |
The air on a normal day
Across 3,653 monitored days from 2016 to 2025, the air in Sweetwater County rated Good on 70% of them, close to the 72% typical of monitored counties, and Moderate on 28%. The median day sat at AQI 45; one day in ten went above 69.
The pollutant setting the AQI on an ordinary day here:
- ozone83%3,029 days
- coarse dust (PM10)13%485 days
- fine particles (PM2.5)3%121 days
Sweetwater County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 266 | 91 | 8 | 0 | 44 | 118 |
| 2024 | 366 | 247 | 109 | 10 | 0 | 45 | 137 |
| 2023 | 365 | 253 | 103 | 9 | 1 | 47 | 211 |
| 2022 | 365 | 285 | 78 | 2 | 1 | 44 | 157 |
| 2021 | 365 | 238 | 117 | 10 | 1 | 45 | 195 |
| 2020 | 366 | 235 | 119 | 12 | 5 | 46 | 1334 |
| 2019 | 365 | 258 | 104 | 3 | 0 | 46 | 133 |
| 2018 | 365 | 210 | 147 | 8 | 1 | 48 | 163 |
| 2017 | 365 | 259 | 101 | 5 | 3 | 46 | 264 |
| 2016 | 366 | 303 | 63 | 0 | 0 | 44 | 100 |
| 2015 | 365 | 256 | 105 | 4 | 0 | 45 | 119 |
| 2014 | 365 | 247 | 110 | 8 | 2 | 46 | 197 |
| 2013 | 365 | 251 | 111 | 3 | 1 | 45 | 309 |
| 2012 | 366 | 210 | 148 | 8 | 1 | 47 | 284 |
| 2011 | 365 | 229 | 131 | 5 | 0 | 48 | 108 |
| 2010 | 365 | 245 | 117 | 3 | 0 | 45 | 112 |
*2025 may be a partial year in EPA's file.
Wyoming compared
- Platte County9/yr
- Albany County6/yr
- Campbell County5/yr
- Sublette County5/yr
- Sheridan County3/yr
- Laramie County3/yr
- Teton County3/yr
- Fremont County2/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.