Bad Air Days in Chelan County, Washington: 11 a Year

11 bad air days a year

Among the worst tenth of monitored US counties. Ranked 75 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (100% particle days).

When the bad days come in Chelan

Most bad days here fall in August and September and October. 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.

Better or worse than it was

In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, 11. It has got worse. The worst recent year was 2018, with 25 bad days on 365 monitored days.

Date	AQI	Main pollutant
2020-09-14	817	PM2.5
2020-09-13	752	PM2.5
2018-08-19	627	PM2.5
2020-09-15	340	PM2.5
2018-08-20	325	PM2.5

Most days, not the worst ones

Across 3,653 monitored days from 2016 to 2025, the air in Chelan County rated Good on 72% of them, close to the 72% typical of monitored counties, and Moderate on 24%. The median day sat at AQI 32; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%3,653 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	254	97	14	9	35	233
2024	366	293	68	5	1	28	158
2023	365	280	80	5	4	34	266
2022	365	246	96	23	15	34	290
2021	365	279	81	5	3	31	195
2020	366	274	80	12	11	28	817
2019	365	258	106	1	0	32	102
2018	365	244	96	25	17	36	627
2017	365	236	108	21	12	37	293
2016	366	284	82	0	0	29	81
2015	362	243	116	3	0	33	148
2014	362	234	120	8	2	33	154
2013	365	230	135	0	0	36	99
2012	366	213	128	25	15	42	443
2011	363	233	123	7	1	33	153
2010	365	251	112	2	0	29	121

*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.