Bad Air Days in Madera County, California: 29 a Year

29 bad air days a year

Among the worst tenth of monitored US counties. Ranked 17 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (36% particle days).

Which months to watch

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.
Sign up for EnviroFlash ozone alerts for this area during the worst months.

The worst days on file

In 2000 to 2009 this county averaged 39 bad days a year; in 2016 to 2025, 29. The air has improved. The worst recent year was 2020, with 53 bad days on 366 monitored days.

Date	AQI	Main pollutant
2020-09-14	275	PM2.5
2020-09-08	227	PM10
2020-09-13	219	PM2.5
2020-08-22	213	PM2.5
2021-10-11	194	PM10

An ordinary day in Madera

Across 3,653 monitored days from 2016 to 2025, the air in Madera County rated Good on 38% of them, less often than the 72% typical of monitored counties, and Moderate on 54%. The median day sat at AQI 57; one day in ten went above 95.

The pollutant setting the AQI on an ordinary day here:

ozone56%2,029 days
fine particles (PM2.5)38%1,394 days
coarse dust (PM10)6%229 days

Madera County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	184	178	3	0	50	136
2024	366	163	178	25	0	52	140
2023	365	162	188	15	1	52	151
2022	365	147	205	13	0	54	136
2021	365	133	197	35	7	58	194
2020	366	104	209	53	19	64	275
2019	365	167	185	13	0	52	140
2018	365	122	208	35	5	58	169
2017	365	117	200	48	6	62	166
2016	366	91	225	50	3	63	156
2015	365	78	240	47	4	64	156
2014	365	63	227	75	15	68	179
2013	365	31	260	74	10	72	190
2012	366	59	226	81	11	68	200
2011	365	20	267	78	15	74	179
2010	364	208	128	28	10	47	201

*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.