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

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 554 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (41% particle days).

When the bad days come in Cumberland

Most bad days here fall in June 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 worst days on file

In 2000 to 2009 this county averaged 7 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2025, with 5 bad days on 365 monitored days.

Date	AQI	Main pollutant
2017-06-12	150	Ozone
2025-08-12	136	Ozone
2021-06-07	129	Ozone
2025-06-05	126	Ozone
2023-10-01	120	PM2.5

The air on a normal day

Across 3,650 monitored days from 2016 to 2025, the air in Cumberland County rated Good on 76% of them, more often than the 72% typical of monitored counties, and Moderate on 23%. The median day sat at AQI 40; one day in ten went above 58.

The pollutant setting the AQI on an ordinary day here:

ozone52%1,891 days
fine particles (PM2.5)46%1,681 days
nitrogen dioxide1%46 days
coarse dust (PM10)1%32 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	271	89	5	0	39	136
2024	366	291	74	1	0	37	119
2023	365	266	96	3	0	40	120
2022	362	323	36	3	0	36	109
2021	365	319	43	3	0	36	129
2020	366	263	103	0	0	42	97
2019	365	208	157	0	0	47	100
2018	365	280	85	0	0	41	100
2017	365	271	92	2	0	40	150
2016	366	288	78	0	0	39	97
2015	365	233	131	1	0	44	108
2014	365	260	103	2	0	41	109
2013	365	232	128	5	0	44	136
2012	366	278	85	3	0	40	126
2011	365	257	105	3	1	40	161
2010	365	277	82	6	2	39	177

*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.