Bad Air Days in Sheridan County, Wyoming: 3 a Year
3 bad air days a year
About the middle of monitored US counties. Ranked 332 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (59% particle days).
When the bad days come in Sheridan
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in July and October and August. 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.
The record for Sheridan
In 2000 to 2009 this county averaged 2 bad days a year; in 2016 to 2025, 3. Not much has changed. The worst recent year was 2024, with 16 bad days on 366 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2024-07-14 | 205 | PM2.5 |
| 2023-09-05 | 175 | PM2.5 |
| 2024-10-06 | 172 | PM2.5 |
| 2024-10-14 | 163 | PM2.5 |
| 2024-10-10 | 162 | PM2.5 |
The air on a normal day
Across 3,646 monitored days from 2016 to 2025, the air in Sheridan County rated Good on 80% of them, more often than the 72% typical of monitored counties, and Moderate on 19%. The median day sat at AQI 41; one day in ten went above 59.
The pollutant setting the AQI on an ordinary day here:
- ozone69%2,524 days
- fine particles (PM2.5)26%950 days
- coarse dust (PM10)5%168 days
Sheridan County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 359 | 320 | 39 | 0 | 0 | 27 | 75 |
| 2024 | 366 | 281 | 69 | 16 | 7 | 44 | 205 |
| 2023 | 365 | 283 | 79 | 3 | 1 | 43 | 175 |
| 2022 | 365 | 270 | 95 | 0 | 0 | 44 | 90 |
| 2021 | 364 | 302 | 55 | 7 | 0 | 40 | 115 |
| 2020 | 366 | 334 | 32 | 0 | 0 | 40 | 100 |
| 2019 | 365 | 315 | 50 | 0 | 0 | 39 | 90 |
| 2018 | 365 | 241 | 121 | 3 | 0 | 46 | 123 |
| 2017 | 365 | 250 | 111 | 4 | 1 | 43 | 157 |
| 2016 | 366 | 326 | 39 | 1 | 0 | 39 | 110 |
| 2015 | 365 | 318 | 45 | 2 | 0 | 40 | 146 |
| 2014 | 365 | 336 | 29 | 0 | 0 | 38 | 84 |
| 2013 | 365 | 325 | 40 | 0 | 0 | 40 | 78 |
| 2012 | 358 | 307 | 51 | 0 | 0 | 23 | 80 |
| 2011 | 362 | 327 | 35 | 0 | 0 | 20 | 91 |
| 2010 | 365 | 320 | 45 | 0 | 0 | 22 | 95 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Platte County9/yr
- Sweetwater County7/yr
- Albany County6/yr
- Campbell County5/yr
- Sublette County5/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.