Bad Air Days in Jefferson County, Oregon: 5 a Year

5 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 196 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 Jefferson

Most bad days here fall in September and August. 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, 5. It has got worse. The worst recent year was 2017, with 9 bad days on 92 monitored days.

Date	AQI	Main pollutant
2020-09-12	1135	PM2.5
2020-09-13	900	PM2.5
2020-09-14	547	PM2.5
2020-09-15	484	PM2.5
2020-09-17	458	PM2.5

An ordinary day in Jefferson

Across 2,824 monitored days from 2017 to 2025, the air in Jefferson County rated Good on 72% of them, close to the 72% typical of monitored counties, and Moderate on 26%. The median day sat at AQI 30; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%2,824 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	361	267	94	0	0	28	90
2024	366	289	76	1	0	26	142
2023	365	266	93	6	3	31	238
2022	365	272	92	1	0	26	108
2021	365	282	77	6	2	28	173
2020	361	258	92	11	8	28	1135
2019	365	261	102	2	0	29	122
2018	184	96	82	6	1	49	156
2017	92	54	29	9	4	37	242
2015	92	60	28	4	1	42	160
2014	82	52	28	2	2	44	184
2013	265	212	53	0	0	31	73
2012	145	116	29	0	0	32	78
2011	165	131	34	0	0	28	99
2010	365	261	103	1	1	33	172

*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.