Counties in Texas by highest daily Air Quality Index (US EPA)

Bexar County had the highest highest daily Air Quality Index (US EPA) of 45 counties in 2023, at 309. Karnes County had the lowest, at 29. The median was 122. Source: the U.S. Environmental Protection Agency.

Highest309Bexar County

Lowest29Karnes County

Median12245 counties

Map of counties, 2023

Under 91
91 to 100
100 to 120
120 to 140
140 to 160
160 and over
No data

index, 2023. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2023

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2023 index	Change on 2022
1	Bexar County	309	+95
2	Harris County	205	+26
3	Denton County	177	-10
4	Dallas County	172	+24
4	Tarrant County	172	0
6	Lubbock County	161	+23
7	Galveston County	159	0
7	Kaufman County	159	+47
9	Brazoria County	156	+37
10	El Paso County	155	-8
11	Collin County	154	+11
11	Jefferson County	154	+25
13	Gregg County	151	+8
14	Hood County	143	-7
15	Cameron County	141	+21
16	Parker County	140	-7
17	Bell County	133	+4
17	Webb County	133	+19
19	McLennan County	129	+29
20	Johnson County	126	-30
21	Potter County	125	+17
22	Montgomery County	122	-4
22	Travis County	122	-7
24	Hunt County	119	+22
24	Smith County	119	-3
26	Ellis County	112	+15
26	Randall County	112	-10
28	Harrison County	111	-70
29	Bowie County	107	+8
30	Brewster County	101	+14
30	Maverick County	101	-6
30	Nueces County	101	-5
30	Orange County	101	-7
34	Navarro County	100	-1
34	Polk County	100	+3
34	Rockwall County	100	0
37	Hidalgo County	95	-41
38	Culberson County	89	-30
38	Kleberg County	89	-44
40	Atascosa County	86	-29
41	Ector County	84	-10
42	Brazos County	79	-15
43	Victoria County	74	0
44	Wilson County	36	-8
45	Karnes County	29	-5

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 18 counties with data in other periods have no value for 2023 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: highest daily AQI (Counties in Texas by highest daily Air Quality Index (US EPA), 2023) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: highest daily AQI, Counties in Texas by highest daily Air Quality Index (US EPA), 2023. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Texas by highest daily Air Quality Index (US EPA), 2023. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Texas by highest daily Air Quality Index (US EPA), 2023 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_texas_by_2023,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Texas by highest daily Air Quality Index (US EPA), 2023}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: highest daily AQI: Counties in Texas by highest daily Air Quality Index (US EPA), 2023
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/texas-counties?period=2023.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -

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Rank Counties in Texas by highest daily Air Quality Index (US EPA) using official data, and cite the source.

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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Bexar County, with 309 in 2023, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Karnes County, with 29 in 2023.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12. 18 counties have no value for 2023 and are not ranked.