Bad Air Days in Grand County, Colorado

Not enough data

EPA monitors in Grand County ran on too few days between 2016 and 2025 to give a fair yearly count (about 38% of days covered). Neighbouring counties below are a better guide.

What actually helps here

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

The record for Grand

The worst recent year was 2021, with 1 bad day on 21 monitored days.

Date	AQI	Main pollutant
2018-06-11	151	Ozone
2021-07-19	119	Ozone
2020-08-22	112	Ozone
2020-08-23	112	Ozone
2018-08-02	101	Ozone

An ordinary day in Grand

Across 1,400 monitored days from 2016 to 2025, the air in Grand County rated Good on 80% of them, more often than the 72% typical of monitored counties, and Moderate on 20%. The median day sat at AQI 45; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

ozone100%1,400 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	158	126	32	0	0	44	77
2024	161	133	28	0	0	45	93
2023	158	131	27	0	0	46	77
2022	174	136	38	0	0	44	80
2021	21	13	7	1	0	48	119
2020	175	134	39	2	0	45	112
2019	118	95	23	0	0	45	80
2018	166	110	54	2	1	47	151
2017	117	109	8	0	0	44	64
2016	152	131	21	0	0	44	80
2015	64	59	5	0	0	38	58

*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.