Bad Air Days in San Juan County, Colorado

Not enough data

EPA monitors in San Juan County ran on too few days between 2016 and 2025 to give a fair yearly count (about 32% of days covered). Neighbouring counties below are a better guide.

Is a purifier worth it here?

EPA monitors here ran too few days to give a fair yearly count. Use AirNow for today's air.

Better or worse than it was

Date	AQI	Main pollutant
2018-06-10	100	PM2.5
2018-06-07	89	PM2.5
2018-06-13	83	PM2.5
2021-08-08	79	PM2.5
2022-06-13	75	PM2.5

The air on a normal day

Across 1,164 monitored days from 2016 to 2025, the air in San Juan County rated Good on 98% of them, more often than the 72% typical of monitored counties, and Moderate on 2%. The median day sat at AQI 9; one day in ten went above 25.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%1,164 days

Every recent year on file

Year	Days monitored	Good	Moderate	Median AQI	Highest AQI
2025*	92	91	1	12	57
2024	121	120	1	9	51
2023	120	120	0	9	50
2022	119	115	4	10	75
2021	119	114	5	9	79
2020	119	115	4	9	73
2019	116	116	0	9	32
2018	118	109	9	10	100
2017	119	119	0	9	49
2016	121	121	0	8	31
2015	121	120	1	8	55
2014	118	118	0	10	37
2013	118	117	1	12	98
2012	119	116	3	13	82
2011	121	121	0	11	48
2010	119	116	3	11	86

*2025 may be a partial year in EPA's file.

Elsewhere in Colorado

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.