Bad Air Days in Klamath County, Oregon: 20 a Year

20 bad air days a year

Among the worst tenth of monitored US counties. Ranked 29 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 Klamath

Most bad days here fall in August and September and July. 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.
With this many bad days, whole-home filtration is worth an HVAC contractor quote.

Better or worse than it was

In 2000 to 2009 this county averaged 21 bad days a year; in 2016 to 2025, 20. Not much has changed. The worst recent year was 2021, with 50 bad days on 365 monitored days.

Date	AQI	Main pollutant
2020-09-12	763	PM2.5
2020-09-13	421	PM2.5
2020-09-11	289	PM2.5
2017-09-03	279	PM2.5
2018-08-03	249	PM2.5

Most days, not the worst ones

Across 3,641 monitored days from 2016 to 2025, the air in Klamath County rated Good on 59% of them, less often than the 72% typical of monitored counties, and Moderate on 36%. The median day sat at AQI 42; one day in ten went above 90.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%3,639 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	235	127	3	0	38	149
2024	366	259	91	16	7	33	207
2023	365	216	137	12	5	39	181
2022	365	222	139	4	2	38	163
2021	365	162	153	50	31	54	237
2020	366	172	148	46	23	52	763
2019	365	230	129	6	0	39	126
2018	360	184	136	40	28	49	249
2017	361	215	120	26	11	39	279
2016	363	250	113	0	0	41	92
2015	365	213	139	13	2	42	205
2014	365	222	139	4	0	42	136
2013	364	178	160	26	4	51	168
2012	360	216	135	9	1	39	152
2011	360	221	125	14	0	36	130
2010	363	229	130	4	0	35	143

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

Elsewhere in Oregon

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.