SmogRank / Countries / United States / Colorado

Most polluted cities in Colorado, United States

18 measured cities ranked by PM2.5, last 7 days. Worst: Thornton at 4.8 µg/m³, #1884 in the world.

#City µg/m³
1Thornton Colorado
4.8
2Westminster low-cost sensorsColorado
4.6
3Greeley Colorado
4.4
4Denver Colorado
4.3
5Fort Collins Colorado
4.2
6Longmont Colorado
4.2
7Northglenn low-cost sensorsColorado
4.1
8Colorado Springs Colorado
4.0
9Pueblo Colorado
3.6
10Windsor Colorado
3.6
11Arvada low-cost sensorsColorado
3.5
12Littleton Colorado
3.4
13Cañon City Colorado
3.0
14Boulder Colorado
2.8
15Ken Caryl Colorado
2.7
16Golden low-cost sensorsColorado
2.2
17Lakewood low-cost sensorsColorado
2.0
18Parker low-cost sensorsColorado
0.8
Good 0–9.0Moderate 9.1+Unhealthy for sensitive groups 35.5+Unhealthy 55.5+Very unhealthy 125.5+Hazardous 225.5+No data

Estimated: cities without a monitor

Colorado 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
Aurora estimated≈ 5 µg/m³Good
Centennial estimated≈ 5 µg/m³Good
Highlands Ranch estimated≈ 5 µg/m³Good
Loveland estimated≈ 3 µg/m³Good
Broomfield estimated≈ 3 µg/m³Good
Grand Junction estimated≈ 3 µg/m³Good
Castle Rock estimated≈ 3 µg/m³Good
Commerce City estimated≈ 5 µg/m³Good
Dakota Ridge estimated≈ 4 µg/m³Good
Englewood estimated≈ 5 µg/m³Good
Security-Widefield estimated≈ 3 µg/m³Good
Wheat Ridge estimated≈ 4 µg/m³Good
Pueblo West estimated≈ 3 µg/m³Good
Fountain estimated≈ 3 µg/m³Good
Lafayette estimated≈ 3 µg/m³Good
Columbine estimated≈ 4 µg/m³Good
Erie estimated≈ 3 µg/m³Good
Evans estimated≈ 4 µg/m³Good
Louisville estimated≈ 3 µg/m³Good
Clifton estimated≈ 3 µg/m³Good
Montrose estimated≈ 1 µg/m³Good
Sherrelwood estimated≈ 3 µg/m³Good
Durango estimated≈ 3 µg/m³Good
Greenwood Village estimated≈ 5 µg/m³Good

Updated 2026-10-01 14:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.