Bad Air Days in Laramie County, Wyoming: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 378 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (43% particle days).

When the bad days come in Laramie

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

What actually helps here

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.

Better or worse than it was

The worst recent year was 2021, with 11 bad days on 364 monitored days.

Date	AQI	Main pollutant
2017-09-04	163	PM2.5
2017-09-01	160	PM2.5
2020-10-06	159	PM2.5
2023-05-19	156	PM2.5
2020-09-26	153	PM2.5

The air on a normal day

Across 3,650 monitored days from 2016 to 2025, the air in Laramie County rated Good on 78% of them, more often than the 72% typical of monitored counties, and Moderate on 21%. The median day sat at AQI 43; one day in ten went above 62.

The pollutant setting the AQI on an ordinary day here:

ozone87%3,172 days
fine particles (PM2.5)11%396 days
coarse dust (PM10)1%52 days
nitrogen dioxide1%27 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	274	90	1	0	45	108
2024	366	271	91	4	1	45	151
2023	365	275	85	5	1	45	156
2022	363	297	66	0	0	42	90
2021	364	261	92	11	0	44	126
2020	366	313	48	5	2	39	159
2019	365	296	69	0	0	43	74
2018	365	288	76	1	0	43	109
2017	365	267	95	3	2	45	163
2016	366	305	61	0	0	43	87
2015	365	302	62	1	1	43	152
2014	365	284	81	0	0	44	97
2013	365	271	91	3	0	43	115
2012	366	225	139	2	0	47	108
2011	365	256	108	1	0	44	101
2010	121	119	2	0	0	23	54

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

Elsewhere in Wyoming

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.