Bad Air Days in Brewster County, Texas: under 1 a Year

under 1 bad air day a year

Rare: among the cleanest-air counties EPA monitors. Ranked 811 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (40% particle days).

Which months to watch

Most bad days here fall in May and March. Averaged over 2016 to 2025.

Is a purifier worth it 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.

Better or worse than it was

In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, under 1. Not much has changed. The worst recent year was 2024, with 2 bad days on 327 monitored days.

Date	AQI	Main pollutant
2025-03-19	164	PM2.5
2024-05-23	112	Ozone
2021-03-23	105	PM2.5
2023-05-10	101	Ozone
2024-05-06	101	Ozone

An ordinary day in Brewster

Across 3,569 monitored days from 2016 to 2025, the air in Brewster County rated Good on 78% of them, more often than the 72% typical of monitored counties, and Moderate on 22%. The median day sat at AQI 42; one day in ten went above 58.

The pollutant setting the AQI on an ordinary day here:

ozone75%2,661 days
fine particles (PM2.5)25%908 days

Brewster County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	272	91	1	1	43	164
2024	327	231	94	2	0	43	112
2023	359	262	96	1	0	43	101
2022	357	266	91	0	0	42	87
2021	356	287	68	1	0	42	105
2020	360	314	46	0	0	41	80
2019	362	278	84	0	0	42	93
2018	363	274	89	0	0	40	97
2017	362	286	76	0	0	42	100
2016	359	297	62	0	0	41	84
2015	358	264	94	0	0	42	87
2014	362	291	71	0	0	42	84
2013	360	266	94	0	0	44	90
2012	365	247	118	0	0	45	97
2011	362	214	136	12	1	47	151
2010	360	279	81	0	0	44	97

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

Elsewhere in Texas

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.