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Eight-Hour Ozone High Value Days for 2021
as of June 16

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
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
Lang C408 12 40848_201_0047April 11 202111:00892
Dallas North No.2 C63/C679 4 6348_113_0075June 16 202110:00881
Houston Aldine C8/AF108/X150 12 848_201_0024April 11 202111:00862
Houston East C1/G316 12 148_201_1034May 29 202111:00862
Pilot Point C1032 4 103248_121_1032June 16 202111:00851
Houston Croquet C409 12 40948_201_0051June 16 202110:00852
Frisco C31/C680 4 3148_085_0005June 16 202111:00811
Baytown Garth C1017 12 101748_201_1017May 29 202111:00811
UH Moody Tower C695 12 69548_201_0695June 15 202109:00801 N
Parker County C76 4 7648_367_0081June 16 202112:00801
Ft. Worth Northwest C13/AH302 4 1348_439_1002June 13 202112:00802
Houston Harvard Street C417 12 41748_201_0417June 15 202109:00791
Dallas Executive Airport C402 4 40248_113_0087June 16 202110:00781
Houston Bayland Park C53/A146 12 5348_201_0055June 15 202109:00781
Park Place C416 12 41648_201_0416June 15 202109:00781
Park Place C416 12 41648_201_0416June 16 202110:00781
Houston Harvard Street C417 12 41748_201_0417April 11 202111:00781
West Houston C554 12 55448_201_0554June 15 202108:00781 N
UH Launch Trailer C1611 12 161148_201_1611June 15 202109:00781 N
Galveston 99th St. C1034/A320/X183 12 103448_167_1034June 14 202111:00771
Granbury C73/C681 4 7348_221_0001June 15 202112:00771
Camp Bullis C58 13 5848_029_0052April 11 202111:00761
Houston Croquet C409 12 40948_201_0051June 15 202108:00762
Houston Harvard Street C417 12 41748_201_0417May 29 202111:00761
Tom Bass C558 12 55848_201_0558June 16 202110:00761 N
Wallisville Road C617 12 61748_201_0617May 29 202111:00761 N
Houston East C1/G316 12 148_201_1034April 11 202110:00762
UH Launch Trailer C1611 12 161148_201_1611April 11 202111:00761 N
Cleburne Airport C77/C682 4 7748_251_0003June 15 202111:00761
Arlington Municipal Airport C61 4 6148_439_3011June 15 202111:00761
Houston North Wayside C405/C1033 12 40548_201_0046April 11 202111:00751
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
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 13 202111:00743
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
West Houston C554 12 55448_201_0554May 14 202112:00741 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
Houston East C1/G316 12 148_201_1034June 15 202110:00742
Hou.DeerPrk2 C35/235/1001/AFH139FP239 12 3548_201_1039May 29 202110:00741
Eagle Mountain Lake C75 4 7548_439_0075June 15 202113:00741
Bunker Hill Village C562 12 56248_201_0562June 15 202108:00731 N
Wallisville Road C617 12 61748_201_0617April 20 202111:00731 N
Cleburne Airport C77/C682 4 7748_251_0003May 6 202111:00731
Conroe Relocated C78/A321 12 7848_339_0078April 12 202110:00731
Arlington Municipal Airport C61 4 6148_439_3011June 16 202109:00731
San Antonio Northwest C23 13 2348_029_0032April 11 202111:00722
Manvel Croix Park C84 12 8448_039_1004June 16 202109:00721
Bulverde Elementary C503 13 50348_091_0503April 11 202111:00721 N
Dallas Hinton St. C401/C60/AH161 4 40148_113_0069June 15 202110:00723
Denton Airport South C56/A163/X157 4 5648_121_0034May 19 202111:00721
Midlothian OFW C52/A137 4 5248_139_0016June 16 202109:00721
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
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
Keller C17 4 1748_439_2003June 13 202113:00722
Keller C17 4 1748_439_2003June 15 202110:00722
Camp Bullis C58 13 5848_029_0052May 7 202110:00711
Manvel Croix Park C84 12 8448_039_1004April 20 202110:00711
El Paso UTEP C12/A125/X151/G125 6 1248_141_0037May 5 202111:00712
Ojo De Agua C1021/FG121/FG221 6 102148_141_1021May 5 202110:00711
Texas City 34th St. C620 12 62048_167_0056April 20 202111:00711 N
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
UH Launch Trailer C1611 12 161148_201_1611April 20 202111:00711 N
Dripping Springs School C614 11 61448_209_0614April 11 202112:00711 N
UH WG Jones Forest C698 12 69848_339_0698April 12 202110:00711 N
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.