Bad Air Days in Clear Creek County, Colorado: 11 a Year

11 bad air days a year

Among the worst tenth of monitored US counties. Ranked 72 of 996 monitored counties, where 1 is worst.

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

Which months to watch

Most bad days here fall in August and July 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.
Sign up for EnviroFlash ozone alerts for this area during the worst months.

Better or worse than it was

The worst recent year was 2018, with 28 bad days on 291 monitored days.

Date	AQI	Main pollutant
2018-06-11	164	Ozone
2018-08-02	156	Ozone
2020-08-23	156	Ozone
2016-06-17	154	Ozone
2021-07-19	154	Ozone

Most days, not the worst ones

Across 3,190 monitored days from 2016 to 2025, the air in Clear Creek County rated Good on 60% of them, less often than the 72% typical of monitored counties, and Moderate on 37%. The median day sat at AQI 49; one day in ten went above 81.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,190 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	315	214	101	0	0	48	100
2024	351	202	139	10	0	49	136
2023	359	204	147	8	0	49	136
2022	359	244	110	5	0	47	126
2021	357	206	127	24	2	49	154
2020	239	140	87	12	2	49	156
2019	294	183	109	2	0	47	126
2018	291	145	118	28	3	51	164
2017	314	173	137	4	0	50	140
2016	311	210	94	7	1	47	154
2015	295	182	107	6	0	48	140
2014	267	169	83	15	0	47	150
2013	122	26	78	18	3	77	156
2012	104	9	58	37	2	90	179
2011	126	31	72	23	2	77	187
2010	105	4	78	23	2	74	161

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

Nearby counties on file

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.