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

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 503 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (0% particle days).

Which months to watch

Most bad days here fall in June and May and July 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 record for Hancock

In 2000 to 2009 this county averaged 15 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2017, with 6 bad days on 365 monitored days.

Date	AQI	Main pollutant
2017-06-12	182	Ozone
2017-04-11	150	Ozone
2017-05-18	140	Ozone
2017-06-11	133	Ozone
2021-06-06	133	Ozone

Most days, not the worst ones

Across 3,649 monitored days from 2016 to 2025, the air in Hancock County rated Good on 90% of them, more often than the 72% typical of monitored counties, and Moderate on 9%. The median day sat at AQI 37; one day in ten went above 51.

The pollutant setting the AQI on an ordinary day here:

ozone90%3,267 days
fine particles (PM2.5)10%377 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	332	29	4	0	35	133
2024	366	334	31	1	0	37	105
2023	365	314	51	0	0	38	93
2022	361	326	34	1	0	36	112
2021	365	324	38	3	0	36	133
2020	366	336	29	1	0	36	105
2019	365	339	25	1	0	37	105
2018	365	331	33	1	0	37	122
2017	365	325	34	6	1	37	182
2016	366	326	38	2	0	38	122
2015	365	315	47	3	0	38	143
2014	365	341	23	1	0	36	105
2013	365	325	37	3	0	38	129
2012	366	331	34	1	0	36	101
2011	365	329	32	4	1	36	166
2010	365	316	44	5	2	37	159

*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, and on why a purifier does not touch ozone in smoke vs ozone.