Bad Air Days in Arlington County, Virginia: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 400 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (11% particle days).

The bad-air season here

Most bad days here fall in July and June and May and August. 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 23 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2016, with 7 bad days on 366 monitored days.

Date	AQI	Main pollutant
2023-06-08	181	PM2.5
2023-06-29	162	PM2.5
2025-07-29	140	Ozone
2016-09-23	133	Ozone
2016-01-25	128	PM2.5

An ordinary day in Arlington

Across 3,653 monitored days from 2016 to 2025, the air in Arlington County rated Good on 84% of them, more often than the 72% typical of monitored counties, and Moderate on 15%. The median day sat at AQI 37; one day in ten went above 57.

The pollutant setting the AQI on an ordinary day here:

ozone66%2,425 days
nitrogen dioxide18%654 days
fine particles (PM2.5)16%568 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	319	44	2	0	37	140
2024	366	309	53	4	0	36	115
2023	365	302	58	5	2	38	181
2022	365	325	40	0	0	37	100
2021	365	306	56	3	0	38	115
2020	366	332	34	0	0	34	90
2019	365	294	70	1	0	40	112
2018	365	298	64	3	0	36	122
2017	365	297	65	3	0	39	115
2016	366	285	74	7	0	38	133
2015	365	271	88	6	0	41	126
2014	365	290	70	5	1	41	154
2013	365	275	89	1	0	39	115
2012	366	260	88	18	3	39	172
2011	365	265	81	19	4	38	187
2010	365	241	97	27	4	43	166

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

Virginia 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.