Bad Air Days in Adams County, Pennsylvania: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 433 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (60% particle days).

The bad-air season here

Most bad days here fall in June and July. 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 27 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2023, with 11 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-08	241	PM2.5
2023-06-29	192	PM2.5
2023-06-07	184	PM2.5
2023-06-30	162	PM2.5
2023-06-28	140	PM2.5

The air on a normal day

Across 3,638 monitored days from 2016 to 2025, the air in Adams County rated Good on 65% of them, less often than the 72% typical of monitored counties, and Moderate on 35%. The median day sat at AQI 45; one day in ten went above 65.

The pollutant setting the AQI on an ordinary day here:

ozone55%1,998 days
fine particles (PM2.5)45%1,638 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	351	261	90	0	0	42	100
2024	366	231	132	3	0	44	131
2023	365	188	166	11	4	50	241
2022	365	221	144	0	0	47	97
2021	364	206	155	3	0	47	129
2020	366	280	86	0	0	42	88
2019	365	243	122	0	0	45	87
2018	365	243	120	2	0	44	105
2017	365	238	126	1	0	45	129
2016	366	239	122	5	0	44	119
2015	365	176	188	1	0	51	101
2014	365	222	141	2	0	45	102
2013	365	173	189	3	0	52	120
2012	365	160	194	11	0	53	146
2011	362	121	236	5	0	55	140
2010	365	142	211	12	2	54	166

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

Pennsylvania 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.