Bad Air Days in Washington County, Pennsylvania: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 557 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (53% particle days).

When the bad days come in Washington

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.

The record for Washington

In 2000 to 2009 this county averaged 25 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 10 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	212	PM2.5
2023-06-29	206	PM2.5
2023-06-05	175	PM2.5
2023-06-30	130	PM2.5
2016-07-12	129	Ozone

Most days, not the worst ones

Across 3,653 monitored days from 2016 to 2025, the air in Washington County rated Good on 49% of them, less often than the 72% typical of monitored counties, and Moderate on 51%. The median day sat at AQI 50; one day in ten went above 66.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)66%2,416 days
ozone34%1,234 days

Washington County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	247	118	0	0	44	100
2024	366	224	141	1	0	44	105
2023	365	180	175	10	3	51	212
2022	365	173	192	0	0	52	87
2021	365	187	177	1	0	49	123
2020	366	221	145	0	0	46	100
2019	365	177	188	0	0	51	95
2018	365	163	200	2	0	52	105
2017	365	117	248	0	0	55	90
2016	366	101	262	3	0	55	129
2015	365	100	258	7	0	55	119
2014	365	79	285	1	0	59	101
2013	365	112	249	4	0	55	147
2012	366	97	251	18	0	58	143
2011	365	106	252	7	0	57	129
2010	365	98	257	10	1	59	154

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