Bad Air Days in Aroostook County, Maine: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 572 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 May and June and August and September. 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.

The worst days on file

In 2000 to 2009 this county averaged under 1 bad days a year; in 2016 to 2025, 2. Not much has changed. The worst recent year was 2025, with 4 bad days on 365 monitored days.

Date	AQI	Main pollutant
2018-08-12	216	PM2.5
2020-08-16	205	PM2.5
2019-05-26	182	PM2.5
2021-05-30	182	PM2.5
2018-05-27	177	PM2.5

The air on a normal day

Across 3,652 monitored days from 2016 to 2025, the air in Aroostook County rated Good on 79% of them, more often than the 72% typical of monitored counties, and Moderate on 20%. The median day sat at AQI 37; one day in ten went above 56.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)58%2,102 days
ozone40%1,456 days
coarse dust (PM10)3%94 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	304	57	4	0	32	131
2024	366	299	67	0	0	35	96
2023	365	277	85	3	0	37	142
2022	364	304	60	0	0	34	80
2021	365	305	58	2	1	35	182
2020	366	316	49	1	1	36	205
2019	365	304	59	2	1	36	182
2018	365	262	101	2	2	42	216
2017	365	257	107	1	0	40	120
2016	366	265	100	1	1	39	169
2015	365	226	139	0	0	44	97
2014	365	221	143	1	0	44	117
2013	365	323	42	0	0	35	94
2012	366	323	43	0	0	35	73
2011	365	325	40	0	0	36	70
2010	365	317	47	1	0	35	101

*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.