SmogRank / World / North America / United States / Wyoming

Most polluted cities in Wyoming, United States

11 measured cities, this year; 1 above the WHO annual guideline. Worst: Sheridan at 6.6 µg/m³, #2,308 in the world.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

Idaho: 10 measured citiesMontana: 10 measured citiesUtah: 21 measured citiesWyoming: 11 measured citiesColorado: 17 measured citiesSouth Dakota: 7 measured citiesNebraska: 8 measured cities#11 Casper: 3.1 µg/m³#7 Laramie: 3.2 µg/m³#8 Ranchettes: 3.2 µg/m³#9 Rawlins: 3.2 µg/m³#10 Worland: 3.2 µg/m³#6 Rock Springs: 3.4 µg/m³#4 Cody: 3.8 µg/m³#5 Riverton: 3.8 µg/m³#3 Lander: 3.9 µg/m³#2 Gillette: 4.3 µg/m³#1 Sheridan: 6.6 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Sheridan 0% 0.75%0
Every measured city in Wyoming, United States, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.
  1. 1Sheridan 0%
  2. 2Cody 0%
  3. 3Worlandlast full day 3 Oct 0%
  4. 4Landerlast full day 3 Oct 0%
  5. 5Gillette 0%
  6. 6Rivertonlast full day 3 Oct 0%
  7. 7Rock Springslast full day 3 Oct 0%
  8. 8Laramie 0%
  9. 8Ranchettes 0%
  10. 8Rawlins 0%
  11. 11Casper 0%
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

Estimated: cities without a monitor

Wyoming cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.

City7-day estimateBand
Cheyenne≈ 2 µg/m³Good

Bad-air episodes in Wyoming

Times when many cities around here had PM2.5 at twice their usual or more on the same days.

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SmogRank, most polluted cities in Wyoming, United States, PM2.5, this year to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/wyoming?w=year.

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.

Updated 2026-10-06 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.