Bad Air Days in San Benito County, California: 4 a Year

4 bad air days a year

About the middle of monitored US counties. Ranked 302 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (70% particle days).

When the bad days come in San Benito

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

What actually helps here

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The record for San Benito

In 2000 to 2009 this county averaged 18 bad days a year; in 2016 to 2025, 4. The air has improved. The worst recent year was 2020, with 17 bad days on 366 monitored days.

Date	AQI	Main pollutant
2020-09-14	174	PM2.5
2020-08-19	172	PM2.5
2020-10-02	164	PM2.5
2020-09-13	159	PM2.5
2020-09-12	158	PM2.5

Most days, not the worst ones

Across 3,653 monitored days from 2016 to 2025, the air in San Benito County rated Good on 81% of them, more often than the 72% typical of monitored counties, and Moderate on 18%. The median day sat at AQI 41; one day in ten went above 58.

The pollutant setting the AQI on an ordinary day here:

ozone80%2,915 days
fine particles (PM2.5)19%711 days
coarse dust (PM10)1%27 days

San Benito County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	334	31	0	0	39	71
2024	366	260	105	1	0	43	105
2023	365	316	48	1	0	40	111
2022	365	297	68	0	0	42	97
2021	365	295	70	0	0	41	100
2020	366	271	78	17	9	41	174
2019	365	318	47	0	0	39	90
2018	365	270	84	11	0	42	143
2017	365	284	79	2	0	41	117
2016	366	298	63	5	0	39	126
2015	365	303	62	0	0	40	93
2014	365	286	75	4	0	42	115
2013	365	270	90	5	0	44	112
2012	366	272	86	8	0	42	133
2011	365	277	86	2	0	43	108
2010	365	288	70	7	0	41	126

*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.