SmogRank / World / North America / United States / Idaho

Most polluted cities in Idaho, United States

12 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Weiser at 8.1 µg/m³, #965 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.

Washington: 56 measured citiesIdaho: 12 measured citiesMontana: 10 measured citiesCalifornia: 123 measured citiesOregon: 43 measured citiesUtah: 20 measured citiesWyoming: 10 measured citiesNevada: 11 measured cities#12 Preston: 3.7 µg/m³#11 Idaho Falls: 3.9 µg/m³#10 Boise: 4.0 µg/m³#9 Moscow: 4.2 µg/m³#8 Twin Falls: 5.0 µg/m³#6 Coeur d'Alene: 5.2 µg/m³#7 Pocatello: 5.2 µg/m³#5 Meridian: 6.4 µg/m³#4 Sandpoint: 6.6 µg/m³#3 Nampa: 7.0 µg/m³#2 Lewiston: 7.9 µg/m³#1 Weiser: 8.1 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Weiser 0% 0.75%0
Every measured city in Idaho, 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. 1Weiserlast full day 1 Oct 0%
  2. 2Lewiston 0%
  3. 3Nampa 0%
  4. 4Sandpoint 0%
  5. 5Meridian 0%
  6. 6Coeur d'Alene 0%
  7. 6Pocatello 0%
  8. 8Twin Falls 0%
  9. 9Moscow 0%
  10. 10Boise 0%
  11. 11Idaho Falls 0%
  12. 12Prestonlast full day 3 Oct 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

Idaho 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
Caldwell≈ 8 µg/m³Good
Lewiston Orchards≈ 6 µg/m³Good
Post Falls≈ 4 µg/m³Good
Eagle Foothills≈ 6 µg/m³Good
Rexburg≈ 3 µg/m³Good
Eagle≈ 6 µg/m³Good
Conda≈ 2 µg/m³Good
Kuna≈ 8 µg/m³Good

Bad-air episodes in Idaho

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

Use this board

SmogRank, most polluted cities in Idaho, United States, PM2.5, last 30 days to 6 Oct 2026, 23:00 UTC, smogrank.com/us/region/idaho?w=30d.

Download top 10 (PNG)

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 23:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.