Bad Air Days in Park County, Colorado: 9 a Year

9 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 107 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (3% particle days).

When the bad days come in Park

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

Is a purifier worth it here?

Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.

The worst days on file

The worst recent year was 2018, with 18 bad days on 324 monitored days.

Date	AQI	Main pollutant
2022-03-08	190	Ozone
2018-06-11	174	Ozone
2020-08-22	161	Ozone
2020-08-23	151	Ozone
2023-04-23	147	Ozone

Most days, not the worst ones

Across 3,088 monitored days from 2016 to 2025, the air in Park County rated Good on 59% of them, less often than the 72% typical of monitored counties, and Moderate on 39%. The median day sat at AQI 49; one day in ten went above 77.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,078 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	203	128	73	2	0	48	105
2024	323	172	139	12	0	50	147
2023	269	137	129	3	0	50	147
2022	261	172	87	2	1	48	190
2021	322	203	103	16	0	48	140
2020	343	187	146	10	2	50	161
2019	312	160	150	2	0	50	101
2018	324	161	145	18	1	51	174
2017	365	237	124	4	0	48	112
2016	366	270	93	3	0	47	133
2015	350	264	82	4	0	45	112
2014	338	232	104	2	0	47	115
2013	304	206	97	1	0	47	101
2012	336	228	99	9	0	47	122
2011	307	219	82	6	0	47	126
2010	191	93	93	5	0	51	133

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