Bad Air Days in Rio Blanco County, Colorado: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 457 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (29% particle days).

The bad-air season here

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

What to buy, and what not to

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.

The record for Rio Blanco

The worst recent year was 2021, with 5 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-02-05	166	Ozone
2021-08-07	156	PM2.5
2024-10-05	142	PM2.5
2021-08-09	140	PM2.5
2024-07-22	133	Ozone

An ordinary day in Rio Blanco

Across 3,287 monitored days from 2016 to 2024, the air in Rio Blanco County rated Good on 67% of them, less often than the 72% typical of monitored counties, and Moderate on 32%. The median day sat at AQI 46; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

ozone72%2,360 days
fine particles (PM2.5)28%925 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2024	366	266	96	4	0	46	142
2023	365	247	113	5	1	47	166
2022	365	243	120	2	0	47	122
2021	365	212	148	5	1	48	156
2020	365	263	99	3	0	45	115
2019	365	252	113	0	0	47	100
2018	365	215	148	2	0	47	108
2017	365	237	128	0	0	46	97
2016	366	271	95	0	0	44	90
2015	365	249	116	0	0	46	100
2014	365	264	101	0	0	45	87
2013	365	187	164	14	6	50	201
2012	366	175	188	3	0	51	103
2011	365	144	217	4	2	53	156
2010	351	241	108	2	0	47	108

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.