Bad Air Days in Dukes County, Massachusetts: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 441 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (4% particle days).

The bad-air season here

Most bad days here fall in July and June and May. 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 14 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 6 bad days on 363 monitored days.

Date	AQI	Main pollutant
2017-06-13	177	Ozone
2017-07-03	174	Ozone
2025-06-24	151	Ozone
2017-06-12	143	Ozone
2023-06-30	133	Ozone

An ordinary day in Dukes

Across 3,558 monitored days from 2016 to 2025, the air in Dukes County rated Good on 93% of them, more often than the 72% typical of monitored counties, and Moderate on 6%. The median day sat at AQI 37; one day in ten went above 48.

The pollutant setting the AQI on an ordinary day here:

ozone95%3,373 days
fine particles (PM2.5)5%185 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	341	327	12	2	1	35	151
2024	357	331	25	1	0	37	108
2023	363	332	25	6	0	38	133
2022	359	338	20	1	0	37	126
2021	356	329	27	0	0	36	100
2020	357	345	11	1	0	37	126
2019	352	329	19	4	0	39	126
2018	360	323	34	3	0	37	108
2017	359	336	19	4	2	37	177
2016	354	335	17	2	0	36	126
2015	260	235	23	2	0	32	112
2014	358	335	23	0	0	35	87
2013	317	283	32	2	0	36	129
2012	252	207	33	12	2	38	187
2011	286	236	41	9	2	41	208
2010	266	209	47	10	2	42	187

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

Massachusetts 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.