Bad Air Days in Cache County, Utah: 8 a Year

8 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 115 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (94% particle days).

When the bad days come in Cache

Most bad days here fall in January and December and August and February. Averaged over 2016 to 2025.

Is a purifier worth it here?

Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.

The record for Cache

In 2000 to 2009 this county averaged 21 bad days a year; in 2016 to 2025, 8. The air has improved. The worst recent year was 2017, with 17 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-02-04	187	Ozone
2017-02-02	172	PM2.5
2023-02-03	166	PM2.5
2020-08-21	162	PM2.5
2017-01-19	160	PM2.5

The air on a normal day

Across 3,653 monitored days from 2016 to 2025, the air in Cache County rated Good on 62% of them, less often than the 72% typical of monitored counties, and Moderate on 36%. The median day sat at AQI 46; one day in ten went above 72.

The pollutant setting the AQI on an ordinary day here:

ozone62%2,256 days
fine particles (PM2.5)37%1,360 days
coarse dust (PM10)1%33 days

Cache County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	241	124	0	0	44	87
2024	366	238	127	1	0	44	101
2023	365	219	138	8	4	48	187
2022	365	223	135	7	1	46	155
2021	365	213	142	10	0	45	129
2020	366	205	152	9	4	48	162
2019	365	247	104	14	0	46	147
2018	365	205	153	7	0	48	133
2017	365	220	128	17	4	47	172
2016	366	241	117	8	0	46	129
2015	365	251	110	4	1	43	159
2014	365	251	101	13	0	45	141
2013	365	137	184	44	16	54	182
2012	366	173	186	7	0	51	116
2011	365	157	198	10	5	52	175
2010	365	119	226	20	6	55	164

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

Utah 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.