Washington County, Nebraska air quality history

Daily Air Quality Index summaries from EPA monitors in Washington, Nebraska, 1999–2025.

87%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

336

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Washington, Nebraska on 336 days. 291 of those days (87%) were in the Good range, and the median daily AQI was 27. That median is lower than the typical monitored county in Nebraska (median 34 across 10 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 336 days. Across the years with fuller monitoring, the share of Good days rose: an average of 67% in 2006–2017 versus 78% in 2023–2025.

Years with fewer than 120 monitored days (2015, 2016, 2018, 2019, 2020, 2021…) are shown in the table but left out of comparisons and trend statements.

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
Fine particles (PM2.5)	336	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	336	291	44	1	0	27	53	132	PM2.5
2024	354	268	86	0	0	34	57	81	PM2.5
2023	360	258	98	3	1	33	60	154	PM2.5
2022	299	280	19	0	0	19	43	64	PM2.5
2021	109	83	25	1	0	37	59	125	PM2.5
2020	110	93	17	0	0	31	53	75	PM2.5
2019	116	95	21	0	0	34	55	78	PM2.5
2018	116	86	30	0	0	39	58	95	PM2.5
2017	121	91	30	0	0	35	54	68	PM2.5
2016	117	96	21	0	0	32	53	66	PM2.5
2015	116	94	22	0	0	33	54	79	PM2.5
2014	109	80	29	0	0	35	59	91	PM2.5
2013	116	79	36	1	0	37	64	101	PM2.5
2012	113	65	48	0	0	46	65	91	PM2.5
2011	113	64	49	0	0	44	63	88	PM2.5
2010	120	74	45	1	0	44	69	106	PM2.5
2009	116	79	36	1	0	39	61	108	PM2.5
2008	103	65	38	0	0	44	60	68	PM2.5
2007	111	69	42	0	0	44	61	100	PM2.5
2006	120	78	41	1	0	41	64	106	PM2.5
2005	115	63	51	1	0	47	70	117	PM2.5
2004	106	68	37	1	0	42	62	105	PM2.5
2003	86	51	35	0	0	43	63	86	PM2.5
2002	94	55	39	0	0	44	69	89	PM2.5
2001	90	47	43	0	0	49	70	80	PM2.5
2000	91	47	44	0	0	48	66	96	PM2.5
1999	63	34	29	0	0	44	67	81	PM2.5

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 Nebraska with a similar median AQI in 2025

All monitored counties in Nebraska

Source: U.S. EPA AirData, “Annual AQI by County” files for 1999–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem