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Eight-Hour Ozone High Value Days for 2021
as of September 20

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2021 in each community where the TCEQ measures ozone. This information is updated hourly. Concentrations are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.) Times shown are in 24-hour format and are Local Standard Time. Our convention is that the time reflects the beginning of the eight-hour average. All ozone measurements are in parts per billion.

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YearSort ByReport Format
Highlight with AQI colors
2021 Sorted by Maximum Value
LocationRegionCAMSAQSDateTimeValuePOC
Eagle Mountain Lake C75 4 7548_439_0075June 16 202112:001141
Ft. Worth Northwest C13/AH302 4 1348_439_1002June 16 202111:001022
Keller C17 4 1748_439_2003June 16 202111:001002
Denton Airport South C56/A163/X157 4 5648_121_0034June 16 202112:00971
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039July 26 202111:00971
Grapevine Fairway C70/A301/X182 4 7048_439_3009June 16 202110:00961
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 16 202110:00953
Ft. Worth Northwest C13/AH302 4 1348_439_1002June 15 202111:00952
Channelview C15/AH115 12 1548_201_0026May 29 202112:00903
Manvel Croix Park C84 12 8448_039_1004September 8 202111:00891
Pilot Point C1032 4 103248_121_1032June 19 202111:00891
Pilot Point C1032 4 103248_121_1032September 7 202111:00891
Lang C408 12 40848_201_0047April 11 202111:00892
HRM-3 Haden Road C603/A114 12 60348_201_0803May 29 202111:00891 N
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039June 19 202109:00891
Dallas North No.2 C63/C679 4 6348_113_0075June 16 202110:00881
Frisco C31/C680 4 3148_085_0005September 7 202111:00871
Houston Croquet C409 12 40948_201_0051June 17 202109:00872
Houston Aldine C8/AF108/X150 12 848_201_0024April 11 202111:00862
Houston Bayland Park C53/A146 12 5348_201_0055June 18 202111:00861
Houston East C1/G316 12 148_201_1034May 29 202111:00862
Frisco C31/C680 4 3148_085_0005June 17 202110:00851
Denton Airport South C56/A163/X157 4 5648_121_0034June 19 202111:00851
Pilot Point C1032 4 103248_121_1032June 16 202111:00851
Pilot Point C1032 4 103248_121_1032June 17 202111:00851
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037July 27 202111:00852
Houston Croquet C409 12 40948_201_0051June 16 202110:00852
Baytown Garth C1017 12 101748_201_1017July 26 202112:00851
Camp Bullis C58 13 5848_029_0052September 10 202111:00841
Denton Airport South C56/A163/X157 4 5648_121_0034July 30 202112:00841
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037July 9 202110:00842
Houston Croquet C409 12 40948_201_0051September 8 202110:00832
Houston Bayland Park C53/A146 12 5348_201_0055September 8 202110:00831
Frisco C31/C680 4 3148_085_0005June 19 202110:00821
Houston Westhollow C410/C3003 12 41048_201_0066June 18 202111:00821
HRM-3 Haden Road C603/A114 12 60348_201_0803July 26 202111:00821 N
Grapevine Fairway C70/A301/X182 4 7048_439_3009July 30 202111:00821
Oyster Creek C1607 12 160748_039_1607September 9 202110:00811 N
Frisco C31/C680 4 3148_085_0005June 16 202111:00811
Denton Airport South C56/A163/X157 4 5648_121_0034July 29 202111:00811
Socorro Hueco C49/F312 6 4948_141_0057July 5 202111:00811
Channelview C15/AH115 12 1548_201_0026July 26 202112:00813
Houston Croquet C409 12 40948_201_0051June 18 202110:00812
Houston Croquet C409 12 40948_201_0051July 28 202111:00812
Houston Harvard Street C417 12 41748_201_0417September 8 202110:00811
West Houston C554 12 55448_201_0554June 18 202109:00811 N
La Porte Sylvan Beach C556 12 55648_201_0556June 19 202109:00811 N
Tom Bass C558 12 55848_201_0558September 8 202110:00811 N
Baytown Garth C1017 12 101748_201_1017May 29 202111:00811
Cleburne Airport C77/C682 4 7748_251_0003September 8 202113:00811
Parker County C76 4 7648_367_0081June 16 202113:00811
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037June 22 202111:00802
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021July 27 202111:00801
UH Moody Tower C695 12 69548_201_0695June 15 202109:00801 N
Cleburne Airport C77/C682 4 7748_251_0003August 3 202111:00801
Eagle Mountain Lake C75 4 7548_439_0075July 29 202112:00801
Ft. Worth Northwest C13/AH302 4 1348_439_1002June 13 202112:00802
Elm Creek Elementary C501 13 50148_029_0501September 10 202111:00791 N
Manvel Croix Park C84 12 8448_039_1004September 9 202111:00791
Lake Jackson C1016 12 101648_039_1016September 9 202111:00791
Park Place C416 12 41648_201_0416June 18 202110:00791
Houston Harvard Street C417 12 41748_201_0417June 15 202109:00791
Seabrook Friendship Park C45 12 4548_201_1050June 19 202109:00791
Grapevine Fairway C70/A301/X182 4 7048_439_3009July 29 202111:00791
Dallas Executive Airport C402 4 40248_113_0087June 16 202110:00781
Denton Airport South C56/A163/X157 4 5648_121_0034June 17 202111:00781
Houston Bayland Park C53/A146 12 5348_201_0055June 15 202109:00781
Houston Bayland Park C53/A146 12 5348_201_0055June 17 202109:00781
Houston Bayland Park C53/A146 12 5348_201_0055July 28 202111:00781
Park Place C416 12 41648_201_0416June 15 202109:00781
Park Place C416 12 41648_201_0416June 16 202110:00781
Park Place C416 12 41648_201_0416June 17 202109:00781
Houston Harvard Street C417 12 41748_201_0417April 11 202111:00781
Houston Harvard Street C417 12 41748_201_0417August 25 202111:00781
West Houston C554 12 55448_201_0554June 15 202108:00781 N
Houston East C1/G316 12 148_201_1034July 26 202111:00782
Clinton C403/C304/AH113 12 40348_201_1035July 26 202111:00783
UH Launch Trailer C1611 12 161148_201_1611June 15 202109:00781 N
Manvel Croix Park C84 12 8448_039_1004July 28 202110:00771
UH Smith Point C1606 12 160648_071_1606June 19 202109:00771 N
Denton Airport South C56/A163/X157 4 5648_121_0034September 7 202111:00771
Galveston 99th St. C1034/A320/X183 12 103448_167_1034June 14 202111:00771
West Houston C554 12 55448_201_0554September 8 202110:00771 N
Granbury C73/C681 4 7348_221_0001June 15 202112:00771
Keller C17 4 1748_439_2003July 27 202112:00772
Keller C17 4 1748_439_2003July 29 202111:00772
San Antonio Northwest C23 13 2348_029_0032September 10 202111:00762
Camp Bullis C58 13 5848_029_0052April 11 202111:00761
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 19 202110:00763
Dallas North No.2 C63/C679 4 6348_113_0075June 17 202110:00761
Dallas North No.2 C63/C679 4 6348_113_0075September 7 202111:00761
Denton Airport South C56/A163/X157 4 5648_121_0034June 18 202109:00761
Denton Airport South C56/A163/X157 4 5648_121_0034July 28 202111:00761
Pilot Point C1032 4 103248_121_1032July 22 202110:00761
Houston Croquet C409 12 40948_201_0051June 15 202108:00762
Houston Harvard Street C417 12 41748_201_0417May 29 202111:00761
West Houston C554 12 55448_201_0554June 17 202109:00761 N
Tom Bass C558 12 55848_201_0558June 16 202110:00761 N
Wallisville Road C617 12 61748_201_0617May 29 202111:00761 N
Wallisville Road C617 12 61748_201_0617July 26 202112:00761 N
UH Moody Tower C695 12 69548_201_0695June 17 202109:00761 N
Lynchburg Ferry C1015/A165 12 101548_201_1015July 26 202112:00761
Houston East C1/G316 12 148_201_1034April 11 202110:00762
Houston East C1/G316 12 148_201_1034June 19 202109:00762
UH Launch Trailer C1611 12 161148_201_1611April 11 202111:00761 N
Cleburne Airport C77/C682 4 7748_251_0003June 15 202111:00761
Eagle Mountain Lake C75 4 7548_439_0075July 7 202112:00761
Ft. Worth Northwest C13/AH302 4 1348_439_1002July 27 202112:00762
Ft. Worth Northwest C13/AH302 4 1348_439_1002July 29 202111:00762
Arlington Municipal Airport C61 4 6148_439_3011June 15 202111:00761
Arlington Municipal Airport C61 4 6148_439_3011September 8 202112:00761
Manvel Croix Park C84 12 8448_039_1004September 7 202110:00751
Socorro Hueco C49/F312 6 4948_141_0057July 25 202111:00751
Texas City 34th St. C620 12 62048_167_0056September 9 202110:00751 N
Houston Aldine C8/AF108/X150 12 848_201_0024June 19 202110:00752
Houston North Wayside C405/C1033 12 40548_201_0046April 11 202111:00751
Park Place C416 12 41648_201_0416July 28 202111:00751
Houston Harvard Street C417 12 41748_201_0417June 19 202109:00751
Bunker Hill Village C562 12 56248_201_0562June 18 202110:00751 N
Bunker Hill Village C562 12 56248_201_0562September 8 202110:00751 N
UH Moody Tower C695 12 69548_201_0695June 18 202110:00751 N
Baytown Garth C1017 12 101748_201_1017April 20 202111:00751
Clinton C403/C304/AH113 12 40348_201_1035May 29 202111:00753
UH Launch Trailer C1611 12 161148_201_1611May 29 202111:00751 N
UH Launch Trailer C1611 12 161148_201_1611June 17 202109:00751 N
Dripping Springs School C614 11 61448_209_0614September 10 202110:00751 N
Beaumont-Downtown C2/A112/C2002 10 248_245_0009August 6 202110:00752
Cleburne Airport C77/C682 4 7748_251_0003July 21 202111:00751
Grapevine Fairway C70/A301/X182 4 7048_439_3009September 7 202111:00751
Lake Jackson C1016 12 101648_039_1016September 8 202110:00741
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 13 202111:00743
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 17 202110:00743
Denton Airport South C56/A163/X157 4 5648_121_0034August 4 202111:00741
Pilot Point C1032 4 103248_121_1032September 10 202111:00741
Socorro Hueco C49/F312 6 4948_141_0057July 17 202108:00741
Skyline Park C72 6 7248_141_0058June 22 202111:00741
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021June 22 202110:00741
Texas City 34th St. C620 12 62048_167_0056March 23 202111:00741 N
Houston Bayland Park C53/A146 12 5348_201_0055June 16 202110:00741
Houston Bayland Park C53/A146 12 5348_201_0055September 7 202110:00741
Houston Westhollow C410/C3003 12 41048_201_0066July 28 202112:00741
Baytown Wetlands Center C552 12 55248_201_0552July 26 202111:00741 N
West Houston C554 12 55448_201_0554May 14 202112:00741 N
Tom Bass C558 12 55848_201_0558June 17 202110:00741 N
UH Moody Tower C695 12 69548_201_0695April 11 202110:00741 N
UH Moody Tower C695 12 69548_201_0695May 29 202111:00741 N
UH Moody Tower C695 12 69548_201_0695September 8 202110:00741 N
HRM-3 Haden Road C603/A114 12 60348_201_0803April 11 202110:00741 N
Houston East C1/G316 12 148_201_1034June 15 202110:00742
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039May 29 202110:00741
UH Launch Trailer C1611 12 161148_201_1611June 18 202110:00741 N
SETRPC Mauriceville 42 C642/C311/C665 10 64248_361_1100September 11 202110:00741 N
Eagle Mountain Lake C75 4 7548_439_0075June 15 202113:00741
Keller C17 4 1748_439_2003July 30 202111:00742
Camp Bullis C58 13 5848_029_0052June 18 202110:00731
Dallas North No.2 C63/C679 4 6348_113_0075June 19 202110:00731
Dallas North No.2 C63/C679 4 6348_113_0075July 30 202110:00731
Denton Airport South C56/A163/X157 4 5648_121_0034September 12 202111:00731
Pilot Point C1032 4 103248_121_1032June 18 202109:00731
Pilot Point C1032 4 103248_121_1032August 5 202109:00731
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037August 3 202109:00732
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037August 6 202110:00732
Chamizal C41/AH126 6 4148_141_0044June 22 202111:00731
Chamizal C41/AH126 6 4148_141_0044July 9 202110:00731
Chamizal C41/AH126 6 4148_141_0044July 27 202110:00731
Socorro Hueco C49/F312 6 4948_141_0057July 23 202109:00731
Houston Westhollow C410/C3003 12 41048_201_0066September 8 202111:00731
Park Place C416 12 41648_201_0416September 8 202110:00731
Houston Harvard Street C417 12 41748_201_0417September 11 202110:00731
West Houston C554 12 55448_201_0554July 28 202111:00731 N
West Houston C554 12 55448_201_0554September 7 202110:00731 N
La Porte Sylvan Beach C556 12 55648_201_0556July 26 202111:00731 N
Tom Bass C558 12 55848_201_0558July 28 202110:00731 N
Bunker Hill Village C562 12 56248_201_0562June 15 202108:00731 N
Wallisville Road C617 12 61748_201_0617April 20 202111:00731 N
HRM-3 Haden Road C603/A114 12 60348_201_0803June 19 202109:00731 N
UH Launch Trailer C1611 12 161148_201_1611September 8 202110:00731 N
Cleburne Airport C77/C682 4 7748_251_0003May 6 202111:00731
Conroe Relocated C78/A321 12 7848_339_0078April 12 202110:00731
Ft. Worth Northwest C13/AH302 4 1348_439_1002July 21 202111:00732
Grapevine Fairway C70/A301/X182 4 7048_439_3009July 27 202111:00731
Arlington Municipal Airport C61 4 6148_439_3011June 16 202109:00731
San Antonio Northwest C23 13 2348_029_0032April 11 202111:00722
Camp Bullis C58 13 5848_029_0052July 29 202110:00721
Elm Creek Elementary C501 13 50148_029_0501September 9 202110:00721 N
Manvel Croix Park C84 12 8448_039_1004June 16 202109:00721
Manvel Croix Park C84 12 8448_039_1004June 17 202110:00721
Oyster Creek C1607 12 160748_039_1607September 7 202111:00721 N
Frisco C31/C680 4 3148_085_0005July 30 202110:00721
Bulverde Elementary C503 13 50348_091_0503April 11 202111:00721 N
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 15 202110:00723
Dallas North No.2 C63/C679 4 6348_113_0075July 29 202110:00721
Denton Airport South C56/A163/X157 4 5648_121_0034May 19 202111:00721
Pilot Point C1032 4 103248_121_1032August 6 202111:00721
Pilot Point C1032 4 103248_121_1032September 12 202111:00721
Midlothian OFW C52/A137 4 5248_139_0016June 16 202109:00721
Skyline Park C72 6 7248_141_0058July 27 202110:00721
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021August 6 202111:00721
Texas City 34th St. C620 12 62048_167_0056September 6 202112:00721 N
Texas City 34th St. C620 12 62048_167_0056September 8 202109:00721 N
Houston Croquet C409 12 40948_201_0051September 7 202110:00722
Houston Bayland Park C53/A146 12 5348_201_0055September 9 202110:00721
Park Place C416 12 41648_201_0416April 11 202111:00721
Park Place C416 12 41648_201_0416April 20 202111:00721
Park Place C416 12 41648_201_0416May 29 202111:00721
Park Place C416 12 41648_201_0416June 19 202108:00721
Houston Harvard Street C417 12 41748_201_0417June 17 202109:00721
Houston Harvard Street C417 12 41748_201_0417June 18 202109:00721
Tom Bass C558 12 55848_201_0558September 9 202111:00721 N
HRM-3 Haden Road C603/A114 12 60348_201_0803April 20 202111:00721 N
Lynchburg Ferry C1015/A165 12 101548_201_1015May 29 202111:00721
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039April 20 202110:00721
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039June 16 202110:00721
Mission C43/AP143 15 4348_215_0043September 9 202110:00721
Cleburne Airport C77/C682 4 7748_251_0003September 12 202111:00721
Ft. Worth Northwest C13/AH302 4 1348_439_1002August 26 202110:00722
Keller C17 4 1748_439_2003June 13 202113:00722
Keller C17 4 1748_439_2003June 15 202110:00722
Keller C17 4 1748_439_2003June 19 202110:00722
Grapevine Fairway C70/A301/X182 4 7048_439_3009June 19 202110:00721
Killeen Skylark Field C1047 9 104748_027_1047September 8 202111:00711
Camp Bullis C58 13 5848_029_0052May 7 202110:00711
Manvel Croix Park C84 12 8448_039_1004April 20 202110:00711
Manvel Croix Park C84 12 8448_039_1004June 18 202109:00711
Manvel Croix Park C84 12 8448_039_1004September 10 202111:00711
Oyster Creek C1607 12 160748_039_1607July 28 202110:00711 N
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069July 21 202110:00713
Denton Airport South C56/A163/X157 4 5648_121_0034September 10 202111:00711
Pilot Point C1032 4 103248_121_1032July 30 202110:00711
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037May 5 202111:00712
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037June 19 202110:00712
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037July 3 202111:00712
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037July 21 202110:00712
Socorro Hueco C49/F312 6 4948_141_0057July 22 202110:00711
Socorro Hueco C49/F312 6 4948_141_0057September 14 202109:00711
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021May 5 202110:00711
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021July 9 202110:00711
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021September 13 202111:00711
Texas City 34th St. C620 12 62048_167_0056April 20 202111:00711 N
Galveston 99th St. C1034/A320/X183 12 103448_167_1034September 9 202109:00711
Northwest Harris Co. C26/A110/X154 12 2648_201_0029September 11 202111:00712
Houston North Wayside C405/C1033 12 40548_201_0046June 19 202109:00711
Lang C408 12 40848_201_0047August 25 202111:00712
Lang C408 12 40848_201_0047September 8 202109:00712
Houston Croquet C409 12 40948_201_0051September 9 202110:00712
Houston Monroe C406 12 40648_201_0062April 20 202110:00711
West Houston C554 12 55448_201_0554June 16 202110:00711 N
Meyer Park C561 12 56148_201_0561April 11 202112:00711 N
HRM-3 Haden Road C603/A114 12 60348_201_0803June 15 202109:00711 N
Baytown Garth C1017 12 101748_201_1017September 19 202110:00711
Seabrook Friendship Park C45 12 4548_201_1050July 26 202111:00711
UH Launch Trailer C1611 12 161148_201_1611April 20 202111:00711 N
UH Launch Trailer C1611 12 161148_201_1611June 19 202109:00711 N
Dripping Springs School C614 11 61448_209_0614April 11 202112:00711 N
SETRPC 43 Jefferson Co Airport C643 10 64348_245_0102June 15 202110:00711
UH WG Jones Forest C698 12 69848_339_0698April 12 202110:00711 N
Eagle Mountain Lake C75 4 7548_439_0075September 9 202111:00711
Ft. Worth Northwest C13/AH302 4 1348_439_1002June 19 202109:00712
Arlington Municipal Airport C61 4 6148_439_3011July 21 202111:00711
POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.
 N - Data from this instrument does not meet EPA quality assurance criteria and cannot be used for regulatory purposes.

Interpreting the AQI

Air Quality Index

Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the Federal Standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA's AirNow web site.

Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.

The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.

AQI Breakpoint Definitions
AQI Range 1hr Ozone
in ppm
8hr Ozone
in ppm
0 - 50 Not Defined 0 - 0.054
51 - 100 Not Defined 0.055 - 0.070
101 - 150 0.125 - 0.164 0.071 - 0.085
151 - 200 0.165 - 0.204 0.086 - 0.105
201 - 300 0.205 - 0.404 0.106 - 0.200
301 - 400 0.405 - 0.504 Not Defined
401 - 500 Not Defined Not Defined
500+ Not Defined Not Defined
  • The AQI for ozone is based on either the peak eight-hour running average since midnight OR the peak one-hour measurement since midnight.

PLEASE NOTE:  This data has not been verified by the TCEQ and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from TCEQ ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.

Following EPA reporting guidelines, negative values may be displayed in our hourly criteria air quality data, down to the negative of the EPA listed Method Detection Limit (MDL) for the particular instrument that made the measurements. The reported concentrations can be negative due to zero drift in the electronic instrument output, data logger channel, or calibration adjustments to the data. Prior to 1/1/2013, slightly negative values were automatically set to zero.