Eight-Hour Ozone High Value Days for 2025
as of July 18
The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2025 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.Use the selection boxes below to customize this report. You may select a different year, a different sorting order, or a different report format. Click on the Generate Report button once you have made your selections.
| 2025 Sorted by Maximum Value | |||||||
|---|---|---|---|---|---|---|---|
| Location | Region | CAMS | AQS | Date | Time | Value | POC |
| Elm Creek Elementary C501 | 13 | 501 | 48_029_0501 | June 24 2025 | 08:00 | 99 | 1 N |
| Galveston 99th St. C1034/A320/X183 | 12 | 1034 | 48_167_1034 | March 1 2025 | 16:00 | 97 | 1 |
| HRM-3 Haden Road C603/A114 | 12 | 603 | 48_201_0803 | June 20 2025 | 16:00 | 96 | 1 N |
| West Houston C554 | 12 | 554 | 48_201_0554 | May 29 2025 | 10:00 | 88 | 1 N |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | May 27 2025 | 10:00 | 88 | 1 N |
| AACOG City of Garden Ridge C505 | 13 | 505 | 48_091_0505 | May 12 2025 | 12:00 | 86 | 1 N |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | March 25 2025 | 10:00 | 86 | 1 N |
| Frisco C31/C680 | 4 | 31 | 48_085_0005 | June 16 2025 | 13:00 | 85 | 1 |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | March 25 2025 | 10:00 | 85 | 1 N |
| Heritage Middle School C622 | 13 | 622 | 48_029_0622 | May 12 2025 | 11:00 | 83 | 1 N |
| Galveston 99th St. C1034/A320/X183 | 12 | 1034 | 48_167_1034 | May 12 2025 | 14:00 | 83 | 1 |
| Killeen Skylark Field C1047 | 9 | 1047 | 48_027_1047 | May 13 2025 | 12:00 | 82 | 1 |
| Galveston 99th St. C1034/A320/X183 | 12 | 1034 | 48_167_1034 | February 1 2025 | 12:00 | 82 | 1 |
| West Houston C554 | 12 | 554 | 48_201_0554 | May 7 2025 | 09:00 | 82 | 1 N |
| Bulverde Elementary C503 | 13 | 503 | 48_091_0503 | May 15 2025 | 11:00 | 81 | 1 N |
| Pilot Point C1032 | 4 | 1032 | 48_121_1032 | May 23 2025 | 10:00 | 81 | 1 |
| Houston Aldine C8/AF108/X150 | 12 | 8 | 48_201_0024 | March 25 2025 | 10:00 | 81 | 2 |
| West Houston C554 | 12 | 554 | 48_201_0554 | May 21 2025 | 09:00 | 80 | 1 N |
| Huffman Wolf Road C563 | 12 | 563 | 48_201_0563 | March 25 2025 | 10:00 | 80 | 1 N |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | April 10 2025 | 11:00 | 80 | 1 |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | April 12 2025 | 11:00 | 80 | 1 |
| Frisco C31/C680 | 4 | 31 | 48_085_0005 | May 23 2025 | 10:00 | 79 | 1 |
| Ascarate Park SE C37/A332/A172/X159 | 6 | 37 | 48_141_0055 | May 11 2025 | 11:00 | 79 | 1 |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | April 10 2025 | 09:00 | 79 | 1 N |
| Lang C408 | 12 | 408 | 48_201_0047 | May 29 2025 | 11:00 | 78 | 2 |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | April 9 2025 | 10:00 | 78 | 1 N |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | June 2 2025 | 09:00 | 78 | 1 N |
| Huffman Wolf Road C563 | 12 | 563 | 48_201_0563 | May 27 2025 | 09:00 | 78 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | May 21 2025 | 11:00 | 78 | 1 N |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | April 9 2025 | 10:00 | 78 | 1 |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | June 2 2025 | 10:00 | 78 | 1 |
| Northwest Harris Co. C26/A110/X154 | 12 | 26 | 48_201_0029 | March 25 2025 | 12:00 | 77 | 2 |
| Mercer Arboretum C557 | 12 | 557 | 48_201_0557 | April 12 2025 | 09:00 | 77 | 1 N |
| Tom Bass C558 | 12 | 558 | 48_201_0558 | March 1 2025 | 12:00 | 77 | 1 N |
| Katy Park C559 | 12 | 559 | 48_201_0559 | May 21 2025 | 09:00 | 77 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 9 2025 | 11:00 | 77 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 11 2025 | 11:00 | 77 | 1 N |
| Bulverde Elementary C503 | 13 | 503 | 48_091_0503 | May 13 2025 | 11:00 | 76 | 1 N |
| Bulverde Elementary C503 | 13 | 503 | 48_091_0503 | May 14 2025 | 11:00 | 76 | 1 N |
| AACOG City of Garden Ridge C505 | 13 | 505 | 48_091_0505 | May 13 2025 | 11:00 | 76 | 1 N |
| Skyline Park C72 | 6 | 72 | 48_141_0058 | May 11 2025 | 11:00 | 76 | 1 |
| Northwest Harris Co. C26/A110/X154 | 12 | 26 | 48_201_0029 | April 9 2025 | 10:00 | 76 | 2 |
| Houston East C1/G316 | 12 | 1 | 48_201_1034 | March 25 2025 | 10:00 | 76 | 2 |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 8 2025 | 12:00 | 76 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | May 13 2025 | 11:00 | 76 | 1 N |
| Granbury C73/C681 | 4 | 73 | 48_221_0001 | April 10 2025 | 12:00 | 76 | 1 |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | March 25 2025 | 11:00 | 76 | 1 |
| Camp Bullis C58 | 13 | 58 | 48_029_0052 | April 11 2025 | 11:00 | 75 | 1 |
| Frisco C31/C680 | 4 | 31 | 48_085_0005 | May 13 2025 | 12:00 | 75 | 1 |
| Dallas North No.2 C63/C679 | 4 | 63 | 48_113_0075 | June 16 2025 | 10:00 | 75 | 1 |
| Texas City 34th St. C620 | 12 | 620 | 48_167_0056 | March 1 2025 | 12:00 | 75 | 1 N |
| Texas City 34th St. C620 | 12 | 620 | 48_167_0056 | May 12 2025 | 13:00 | 75 | 1 N |
| Longview C19/A127/C644 | 5 | 19 | 48_183_0001 | April 9 2025 | 13:00 | 75 | 2 |
| Lang C408 | 12 | 408 | 48_201_0047 | March 25 2025 | 11:00 | 75 | 2 |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | April 10 2025 | 10:00 | 75 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 21 2025 | 11:00 | 75 | 1 N |
| Laredo College C44 | 16 | 44 | 48_479_0016 | May 15 2025 | 11:00 | 75 | 1 N |
| Killeen Skylark Field C1047 | 9 | 1047 | 48_027_1047 | April 12 2025 | 11:00 | 74 | 1 |
| Government Canyon C1610 | 13 | 1610 | 48_029_1610 | April 11 2025 | 11:00 | 74 | 1 N |
| Government Canyon C1610 | 13 | 1610 | 48_029_1610 | April 21 2025 | 11:00 | 74 | 1 N |
| Government Canyon C1610 | 13 | 1610 | 48_029_1610 | May 21 2025 | 10:00 | 74 | 1 N |
| Lockhart C1604 | 11 | 1604 | 48_055_1604 | April 9 2025 | 11:00 | 74 | 1 N |
| Pilot Point C1032 | 4 | 1032 | 48_121_1032 | May 13 2025 | 12:00 | 74 | 1 |
| Northwest Harris Co. C26/A110/X154 | 12 | 26 | 48_201_0029 | April 12 2025 | 11:00 | 74 | 2 |
| West Houston C554 | 12 | 554 | 48_201_0554 | March 25 2025 | 10:00 | 74 | 1 N |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | April 12 2025 | 09:00 | 74 | 1 N |
| Huffman Wolf Road C563 | 12 | 563 | 48_201_0563 | April 10 2025 | 09:00 | 74 | 1 N |
| Eagle Mountain Lake C75 | 4 | 75 | 48_439_0075 | May 23 2025 | 11:00 | 74 | 1 |
| Ft. Worth Northwest C13/AH302 | 4 | 13 | 48_439_1002 | May 23 2025 | 10:00 | 74 | 2 |
| Laredo College C44 | 16 | 44 | 48_479_0016 | May 12 2025 | 10:00 | 74 | 1 N |
| Calaveras Lake C59 | 13 | 59 | 48_029_0059 | May 12 2025 | 11:00 | 73 | 1 |
| Heritage Middle School C622 | 13 | 622 | 48_029_0622 | April 21 2025 | 11:00 | 73 | 1 N |
| Heritage Middle School C622 | 13 | 622 | 48_029_0622 | May 20 2025 | 13:00 | 73 | 1 N |
| Seguin Outdoor Learning Center C506 | 13 | 506 | 48_187_0506 | May 12 2025 | 12:00 | 73 | 1 N |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | April 9 2025 | 09:00 | 73 | 1 N |
| Bunker Hill Village C562 | 12 | 562 | 48_201_0562 | May 21 2025 | 09:00 | 73 | 1 N |
| Rockwall Heath C69 | 4 | 69 | 48_397_0001 | June 16 2025 | 11:00 | 73 | 1 |
| Grapevine Fairway C70/A301/X182 | 4 | 70 | 48_439_3009 | May 23 2025 | 10:00 | 73 | 1 |
| Fair Oaks Ranch C502 | 13 | 502 | 48_029_0502 | April 11 2025 | 12:00 | 72 | 1 N |
| Heritage Middle School C622 | 13 | 622 | 48_029_0622 | April 11 2025 | 11:00 | 72 | 1 N |
| Government Canyon C1610 | 13 | 1610 | 48_029_1610 | May 12 2025 | 10:00 | 72 | 1 N |
| Frisco C31/C680 | 4 | 31 | 48_085_0005 | May 14 2025 | 10:00 | 72 | 1 |
| Pilot Point C1032 | 4 | 1032 | 48_121_1032 | July 9 2025 | 12:00 | 72 | 1 |
| Lang C408 | 12 | 408 | 48_201_0047 | May 7 2025 | 09:00 | 72 | 2 |
| Houston Harvard Street C417 | 12 | 417 | 48_201_0417 | March 25 2025 | 11:00 | 72 | 1 |
| West Houston C554 | 12 | 554 | 48_201_0554 | April 9 2025 | 09:00 | 72 | 1 N |
| HRM-3 Haden Road C603/A114 | 12 | 603 | 48_201_0803 | March 25 2025 | 10:00 | 72 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 12 2025 | 11:00 | 72 | 1 N |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | May 20 2025 | 11:00 | 72 | 1 N |
| Waco Mazanec C1037 | 9 | 1037 | 48_309_1037 | April 9 2025 | 11:00 | 72 | 1 |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | April 16 2025 | 10:00 | 72 | 1 |
| Conroe Relocated C78/A321 | 12 | 78 | 48_339_0078 | June 9 2025 | 11:00 | 72 | 1 |
| Ft. Worth Northwest C13/AH302 | 4 | 13 | 48_439_1002 | April 10 2025 | 11:00 | 72 | 2 |
| Keller C17 | 4 | 17 | 48_439_2003 | March 1 2025 | 11:00 | 72 | 2 |
| Killeen Skylark Field C1047 | 9 | 1047 | 48_027_1047 | April 9 2025 | 11:00 | 71 | 1 |
| Killeen Skylark Field C1047 | 9 | 1047 | 48_027_1047 | May 14 2025 | 11:00 | 71 | 1 |
| Camp Bullis C58 | 13 | 58 | 48_029_0052 | May 15 2025 | 11:00 | 71 | 1 |
| Camp Bullis C58 | 13 | 58 | 48_029_0052 | May 21 2025 | 10:00 | 71 | 1 |
| Elm Creek Elementary C501 | 13 | 501 | 48_029_0501 | April 21 2025 | 11:00 | 71 | 1 N |
| Fair Oaks Ranch C502 | 13 | 502 | 48_029_0502 | April 10 2025 | 11:00 | 71 | 1 N |
| Government Canyon C1610 | 13 | 1610 | 48_029_1610 | May 13 2025 | 11:00 | 71 | 1 N |
| Lockhart C1604 | 11 | 1604 | 48_055_1604 | April 8 2025 | 10:00 | 71 | 1 N |
| Lockhart C1604 | 11 | 1604 | 48_055_1604 | May 20 2025 | 12:00 | 71 | 1 N |
| AACOG City of Garden Ridge C505 | 13 | 505 | 48_091_0505 | April 11 2025 | 11:00 | 71 | 1 N |
| AACOG City of Garden Ridge C505 | 13 | 505 | 48_091_0505 | May 15 2025 | 11:00 | 71 | 1 N |
| Dallas Executive Airport C402 | 4 | 402 | 48_113_0087 | May 7 2025 | 11:00 | 71 | 1 |
| Ascarate Park SE C37/A332/A172/X159 | 6 | 37 | 48_141_0055 | June 16 2025 | 11:00 | 71 | 1 |
| Ascarate Park SE C37/A332/A172/X159 | 6 | 37 | 48_141_0055 | July 15 2025 | 11:00 | 71 | 1 |
| Houston Aldine C8/AF108/X150 | 12 | 8 | 48_201_0024 | April 12 2025 | 10:00 | 71 | 2 |
| Northwest Harris Co. C26/A110/X154 | 12 | 26 | 48_201_0029 | April 10 2025 | 10:00 | 71 | 2 |
| Houston Harvard Street C417 | 12 | 417 | 48_201_0417 | May 29 2025 | 11:00 | 71 | 1 |
| Crosby Library C553 | 12 | 553 | 48_201_0553 | April 10 2025 | 08:00 | 71 | 1 N |
| La Porte Sylvan Beach C556 | 12 | 556 | 48_201_0556 | May 12 2025 | 12:00 | 71 | 1 N |
| Atascocita C560 | 12 | 560 | 48_201_0560 | March 25 2025 | 09:00 | 71 | 1 N |
| Meyer Park C561 | 12 | 561 | 48_201_0561 | May 27 2025 | 10:00 | 71 | 1 N |
| Bunker Hill Village C562 | 12 | 562 | 48_201_0562 | May 29 2025 | 10:00 | 71 | 1 N |
| Baytown Garth C1017 | 12 | 1017 | 48_201_1017 | March 25 2025 | 10:00 | 71 | 1 |
| Dripping Springs School C614 | 11 | 614 | 48_209_0614 | April 10 2025 | 11:00 | 71 | 1 N |
| Mission C43/AP143 | 15 | 43 | 48_215_0043 | April 8 2025 | 10:00 | 71 | 1 |
| Mission C43/AP143 | 15 | 43 | 48_215_0043 | May 12 2025 | 10:00 | 71 | 1 |
| Cleburne Airport C77/C682 | 4 | 77 | 48_251_0003 | April 10 2025 | 12:00 | 71 | 1 |
| Waco Mazanec C1037 | 9 | 1037 | 48_309_1037 | May 13 2025 | 11:00 | 71 | 1 |
| Grapevine Fairway C70/A301/X182 | 4 | 70 | 48_439_3009 | July 9 2025 | 11:00 | 71 | 1 |
| St. Edwards University C1605 | 11 | 1605 | 48_453_1605 | April 8 2025 | 11:00 | 71 | 1 N |
| St. Edwards University C1605 | 11 | 1605 | 48_453_1605 | April 11 2025 | 11:00 | 71 | 1 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
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.