Bad Air Days in Sutter County, California: 14 a Year

14 bad air days a year

Among the worst tenth of monitored US counties. Ranked 54 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (53% particle days).

Which months to watch

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

What to buy, and what not to

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.

Better or worse than it was

In 2000 to 2009 this county averaged 32 bad days a year; in 2016 to 2025, 14. The air has improved. The worst recent year was 2018, with 35 bad days on 365 monitored days.

Date	AQI	Main pollutant
2018-11-15	420	PM2.5
2020-09-13	356	PM2.5
2018-11-16	296	PM2.5
2020-09-12	288	PM2.5
2018-11-17	265	PM2.5

Most days, not the worst ones

Across 3,648 monitored days from 2016 to 2025, the air in Sutter County rated Good on 43% of them, less often than the 72% typical of monitored counties, and Moderate on 53%. The median day sat at AQI 53; one day in ten went above 83.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)54%1,978 days
ozone45%1,654 days

Sutter County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	230	134	0	0	47	100
2024	366	195	166	5	0	49	115
2023	363	192	168	3	0	49	105
2022	364	154	205	5	0	52	119
2021	364	102	240	22	5	59	175
2020	366	162	173	31	16	53	356
2019	365	200	163	2	0	48	110
2018	365	94	236	35	13	58	420
2017	365	128	228	9	0	56	130
2016	366	115	219	32	0	58	147
2015	365	157	200	8	0	54	119
2014	365	132	220	13	1	55	156
2013	365	176	180	9	0	52	126
2012	366	159	190	17	0	53	150
2011	365	92	252	21	1	58	152
2010	365	163	198	4	1	52	177

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

California compared

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.