Harris County, Texas air quality history

Daily Air Quality Index summaries from EPA monitors in Harris, Texas, 1980–2025.

11%

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 Harris, Texas on 365 days. 40 of those days (11%) were in the Good range, and the median daily AQI was 62. That median is higher than the typical monitored county in Texas (median 43.5 across 44 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 241 days. Across the years with fuller monitoring, the share of Good days fell: an average of 34% in 1980–1982 versus 12% 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
Fine particles (PM2.5)	241	66%
Ozone	99	27%
Coarse particles (PM10)	24	7%
Nitrogen dioxide (NO₂)	1	<1%

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	40	287	28	10	0	62	101	172	PM2.5
2024	366	50	269	33	13	1	61	108	201	PM2.5
2023	365	44	273	38	9	1	64	121	205	PM2.5
2022	365	57	281	22	5	0	60	93	179	PM2.5
2021	365	64	276	18	7	0	58	90	179	PM2.5
2020	366	109	240	15	2	0	56	82	190	PM2.5
2019	365	91	247	22	4	1	56	93	202	PM2.5
2018	365	102	236	19	7	1	56	87	204	PM2.5
2017	365	107	238	18	2	0	54	80	177	PM2.5
2016	366	118	231	16	1	0	55	80	159	PM2.5
2015	365	88	238	27	11	1	58	101	203	PM2.5
2014	365	68	289	7	1	0	58	79	151	PM2.5
2013	365	78	268	17	2	0	57	82	197	PM2.5
2012	366	51	280	27	6	2	59	97	217	PM2.5
2011	365	42	278	35	10	0	60	108	190	PM2.5
2010	365	57	270	27	11	0	60	101	179	PM2.5
2009	365	45	291	19	8	2	60	96	205	PM2.5
2008	365	39	289	30	6	1	64	101	201	PM2.5
2007	365	22	298	30	15	0	67	112	200	PM2.5
2006	365	27	273	44	13	8	67	126	222	PM2.5
2005	363	22	257	46	32	6	67	154	214	PM2.5
2004	366	62	241	30	27	6	63	147	221	PM2.5
2003	365	46	250	32	25	12	64	151	226	PM2.5
2002	365	62	246	31	19	7	61	133	241	PM2.5
2001	365	69	235	31	17	13	62	143	235	PM2.5
2000	366	42	251	31	26	16	64	159	241	PM2.5
1999	365	132	143	36	30	24	60	185	271	Ozone
1998	365	158	130	38	20	19	54	151	271	Ozone
1997	365	188	103	28	26	20	50	169	249	Ozone
1996	366	196	112	27	18	13	49	133	261	Ozone
1995	365	166	100	33	31	35	54	200	254	Ozone
1994	365	167	115	36	34	13	54	159	234	Ozone
1993	365	206	114	17	15	13	47	133	224	Ozone
1992	366	176	131	29	18	12	54	133	264	Ozone
1991	365	179	118	31	21	16	52	154	257	NO2
1990	365	161	116	35	26	27	57	182	268	Ozone
1989	365	186	106	29	24	20	48	174	253	Ozone
1988	366	140	123	37	40	26	58	187	277	Ozone
1987	365	116	135	46	37	31	68	187	240	Ozone
1986	365	139	132	40	31	23	58	177	238	Ozone
1985	365	147	123	32	30	33	58	195	296	Ozone
1984	366	135	125	45	35	26	67	190	266	Ozone
1983	365	106	119	49	44	47	79	208	295	Ozone
1982	365	155	104	40	29	37	57	201	274	Ozone
1981	365	118	130	52	27	38	68	202	292	Ozone
1980	364	102	138	52	24	48	77	212	297	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 Texas with a similar median AQI in 2025

All monitored counties in Texas

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