Bad Air Days in Washoe County, Nevada: 10 a Year

10 bad air days a year

Among the worst tenth of monitored US counties. Ranked 82 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (61% particle days).

When the bad days come in Washoe

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

What actually helps 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.
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.

The record for Washoe

In 2000 to 2009 this county averaged 10 bad days a year; in 2016 to 2025, 10. Not much has changed. The worst recent year was 2021, with 35 bad days on 365 monitored days.

Date	AQI	Main pollutant
2021-08-23	333	PM2.5
2021-08-24	285	PM2.5
2021-08-22	276	PM2.5
2020-09-13	265	PM2.5
2022-09-14	259	PM2.5

The air on a normal day

Across 3,653 monitored days from 2016 to 2025, the air in Washoe County rated Good on 51% of them, less often than the 72% typical of monitored counties, and Moderate on 46%. The median day sat at AQI 50; one day in ten went above 77.

The pollutant setting the AQI on an ordinary day here:

ozone68%2,466 days
fine particles (PM2.5)30%1,100 days
coarse dust (PM10)2%56 days
nitrogen dioxide1%31 days

Washoe County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	183	180	2	0	50	112
2024	366	188	174	4	0	50	119
2023	365	191	174	0	0	50	97
2022	365	180	176	9	8	51	259
2021	365	174	156	35	19	51	333
2020	366	193	149	24	13	50	265
2019	365	214	151	0	0	48	97
2018	365	177	169	19	0	51	146
2017	365	165	196	4	0	52	126
2016	366	203	156	7	0	49	108
2015	365	165	188	12	0	52	115
2014	365	143	207	15	8	54	935
2013	365	121	209	35	18	57	939
2012	366	124	222	20	8	58	939
2011	365	197	164	4	0	49	136
2010	365	221	140	4	0	47	122

*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.