Air Quality Rankings for Colorado 2026

Colorado has 32 cities with EPA air quality data. San Juan, Colorado has the cleanest air with a 5-year average AQI of 9. Denver, Colorado has the highest AQI at 54.

#	City	5yr Avg AQI	Current AQI	Worst Pollutant	Trend	Grade
1	San Juan, Colorado	9	9	PM2.5	Stable	B
2	Fremont, Colorado	13	12	PM10	Stable	A
3	Pitkin, Colorado	13	13	PM10	Stable	B
4	Routt, Colorado	14	13	PM10	Stable	A
5	Alamosa, Colorado	14	22	PM10	Improving	A
6	Prowers, Colorado	17	19	PM10	Stable	B
7	Jackson, Colorado	21	45	PM2.5	Worsening	B
8	Pueblo, Colorado	27	43	PM2.5	Worsening	B
9	Archuleta, Colorado	39	35	Ozone	Worsening	C
10	Moffat, Colorado	42	42	Ozone	Worsening	C
11	Delta, Colorado	42	44	Ozone	Worsening	C
12	Montezuma, Colorado	44	44	Ozone	Stable	C
13	Mesa, Colorado	45	46	Ozone	Improving	B
14	Gilpin, Colorado	46	47	Ozone	Worsening	C
15	Grand, Colorado	46	46	Ozone	Worsening	C
16	Gunnison, Colorado	46	46	Ozone	Stable	C
17	La Plata, Colorado	46	46	Ozone	Stable	C
18	Arapahoe, Colorado	46	47	Ozone	Stable	C
19	El Paso, Colorado	46	47	Ozone	Stable	C
20	San Miguel, Colorado	47	47	Ozone	Worsening	C
21	Rio Blanco, Colorado	47	47	Ozone	Stable	C
22	Jefferson, Colorado	47	49	Ozone	Stable	D
23	Douglas, Colorado	47	49	Ozone	Worsening	D
24	Clear Creek, Colorado	48	49	Ozone	Stable	C
25	Park, Colorado	49	50	Ozone	Worsening	C
26	Garfield, Colorado	50	54	Ozone	Worsening	C
27	Adams, Colorado	50	51	Ozone	Worsening	C
28	Boulder, Colorado	50	50	Ozone	Worsening	D
29	Larimer, Colorado	51	51	Ozone	Stable	C
30	Chaffee, Colorado	53	58	Ozone	Worsening	C
31	Weld, Colorado	53	55	Ozone	Worsening	D
32	Denver, Colorado	54	54	PM2.5	Stable	C

Air quality data for Colorado is sourced from the EPA Air Quality System (AQS), which monitors outdoor air quality at thousands of stations nationwide.
— EPA Air Quality System

Frequently Asked Questions

San Juan, Colorado has the best air quality in Colorado with a 5-year average AQI of 9 and a grade of B.

Colorado has 32 cities with EPA air quality monitoring data in our database, covering multiple years of AQI measurements.

The Air Quality Index (AQI) measures five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Lower AQI values indicate cleaner air — 0-50 is "Good," while 150+ is "Unhealthy."

Sources: EPA Air Quality System (AQS)

Cities ranked by 5-year average AQI (lower is better). Grades factor in average AQI, trend direction, unhealthy days, and dominant pollutant.

Cleanest Cities Nationwide →All Air Quality in Colorado →