Bad Air Days in Durham County, North Carolina: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 853 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (100% particle days).

The bad-air season here

Most bad days here fall in June and July and November. Averaged over 2016 to 2025.

What to buy, and what not to

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 worst days on file

In 2000 to 2009 this county averaged 20 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2023, with 3 bad days on 361 monitored days.

Date	AQI	Main pollutant
2023-06-29	121	PM2.5
2016-11-18	119	PM2.5
2023-06-30	104	PM2.5
2023-07-18	104	PM2.5
2017-05-16	100	Ozone

An ordinary day in Durham

Across 3,639 monitored days from 2016 to 2025, the air in Durham County rated Good on 62% of them, less often than the 72% typical of monitored counties, and Moderate on 38%. The median day sat at AQI 46; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)67%2,456 days
ozone32%1,169 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	262	103	0	0	42	77
2024	366	170	196	0	0	51	97
2023	361	252	106	3	0	44	121
2022	365	273	92	0	0	42	93
2021	365	238	127	0	0	44	90
2020	364	276	88	0	0	40	97
2019	364	207	157	0	0	47	87
2018	358	191	167	0	0	48	100
2017	365	191	174	0	0	49	100
2016	366	194	171	1	0	49	119
2015	359	202	157	0	0	48	87
2014	365	217	148	0	0	46	90
2013	365	244	121	0	0	43	87
2012	365	214	144	7	1	47	151
2011	365	178	184	3	0	51	122
2010	364	151	205	8	0	53	129

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

Elsewhere in North Carolina

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.