Washington County, Pennsylvania air quality history

Daily Air Quality Index summaries from EPA monitors in Washington, Pennsylvania, 1980–2025.

68%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

365

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Washington, Pennsylvania on 365 days. 247 of those days (68%) were in the Good range, and the median daily AQI was 44. That median is higher than the typical monitored county in Pennsylvania (median 40 across 38 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 200 days. Across the years with fuller monitoring, the share of Good days fell: an average of 73% in 1980–1982 versus 59% in 2023–2025.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Ozone	200	55%
Fine particles (PM2.5)	165	45%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	365	247	118	0	0	0	44	62	100	Ozone
2024	366	224	141	1	0	0	44	69	105	Ozone
2023	365	180	175	7	1	2	51	72	212	PM2.5
2022	365	173	192	0	0	0	52	64	87	PM2.5
2021	365	187	177	1	0	0	49	67	123	PM2.5
2020	366	221	145	0	0	0	46	61	100	PM2.5
2019	365	177	188	0	0	0	51	66	95	PM2.5
2018	365	163	200	2	0	0	52	67	105	PM2.5
2017	365	117	248	0	0	0	55	68	90	PM2.5
2016	366	101	262	3	0	0	55	68	129	PM2.5
2015	365	100	258	7	0	0	55	75	119	PM2.5
2014	365	79	285	1	0	0	59	74	101	PM2.5
2013	365	112	249	4	0	0	55	72	147	PM2.5
2012	366	97	251	18	0	0	58	84	143	PM2.5
2011	365	106	252	7	0	0	57	78	129	PM2.5
2010	365	98	257	9	1	0	59	81	154	PM2.5
2009	365	73	290	2	0	0	58	76	101	PM2.5
2008	366	141	214	11	0	0	54	78	136	PM2.5
2007	365	102	237	24	2	0	58	92	157	PM2.5
2006	365	148	196	21	0	0	54	90	150	PM2.5
2005	365	91	240	29	5	0	60	97	166	PM2.5
2004	366	110	240	16	0	0	56	89	148	PM2.5
2003	365	100	244	15	5	1	58	90	217	PM2.5
2002	365	123	198	24	19	1	58	119	204	PM2.5
2001	365	94	219	41	11	0	60	112	185	PM2.5
2000	366	92	254	17	3	0	58	87	200	PM2.5
1999	365	127	190	33	14	1	56	112	204	PM2.5
1998	365	226	65	39	30	5	42	143	212	Ozone
1997	365	257	62	32	12	2	40	112	202	NO2
1996	366	269	62	29	6	0	39	100	195	NO2
1995	365	264	61	22	18	0	39	108	197	NO2
1994	363	258	64	30	11	0	42	101	192	NO2
1993	365	247	72	37	9	0	42	112	185	NO2
1992	366	288	63	14	1	0	38	73	179	NO2
1991	365	239	87	25	13	1	43	101	202	NO2
1990	365	278	63	19	5	0	39	84	190	NO2
1989	365	258	83	19	5	0	40	90	179	NO2
1988	366	240	72	18	25	11	42	147	244	NO2
1987	365	219	106	26	13	1	44	101	212	NO2
1986	365	241	97	21	6	0	43	93	197	NO2
1985	365	242	88	28	6	1	43	100	204	Ozone
1984	359	286	46	17	10	0	35	84	179	Ozone
1983	350	258	48	22	17	5	36	115	219	Ozone
1982	363	259	67	30	6	1	41	101	201	Ozone
1981	339	272	41	17	5	4	36	80	225	NO2
1980	347	238	59	30	16	4	40	122	212	Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Pennsylvania with a similar median AQI in 2025

All monitored counties in Pennsylvania

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem