Bad Air Days in Gunnison County, Colorado: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 580 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (0% particle days).

When the bad days come in Gunnison

Most bad days here fall in May and August and June and April. Averaged over 2016 to 2025.

Is a purifier worth it here?

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

Better or worse than it was

In 2000 to 2009 this county averaged 3 bad days a year; in 2016 to 2025, 2. Not much has changed. The worst recent year was 2018, with 5 bad days on 365 monitored days.

Date	AQI	Main pollutant
2018-06-11	156	Ozone
2017-04-22	140	Ozone
2018-06-12	115	Ozone
2018-08-02	115	Ozone
2020-08-22	115	Ozone

Most days, not the worst ones

Across 3,614 monitored days from 2016 to 2025, the air in Gunnison County rated Good on 74% of them, close to the 72% typical of monitored counties, and Moderate on 26%. The median day sat at AQI 46; one day in ten went above 66.

The pollutant setting the AQI on an ordinary day here:

ozone99%3,562 days
coarse dust (PM10)1%52 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	264	99	1	0	46	115
2024	366	243	123	0	0	47	100
2023	363	251	112	0	0	46	93
2022	365	281	82	2	0	46	108
2021	365	262	102	1	0	46	101
2020	335	270	62	3	0	44	115
2019	362	264	96	2	0	46	101
2018	365	235	125	5	1	47	156
2017	363	275	87	1	0	45	140
2016	366	316	50	0	0	44	87
2015	365	283	79	3	0	44	101
2014	365	307	58	0	0	44	90
2013	364	266	97	1	0	45	117
2012	366	254	107	5	0	46	136
2011	365	289	70	6	0	44	119
2010	365	308	55	2	0	42	129

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

Colorado compared

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, and on why a purifier does not touch ozone in smoke vs ozone.