One-Hour Ozone High Value Days for 2025
as of February 10
In July 1997, the U. S. Environmental Protection Agency (EPA) announced a new National Ambient Air Quality Standard for ground-level ozone. The EPA is phasing out and replacing the previous one-hour standard with a new eight-hour standard to protect public health against longer exposure to the air pollutant.
A community will meet the new standard when the three-year average of the fourth-highest daily maximum eight-hour concentration measured at each monitoring site is less than 85 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. All times shown are in 24-hour format and are Local Standard Time. These times correspond to the beginning of the hourly average.
The table below lists the one-hour ozone concentrations measured in 2025 in each community where TCEQ measures ozone that are equal to or higher than 125 parts per billion. All ozone measurements are in parts per billion. Concentrations are color-highlighted based on the EPA-defined Air Quality Index colors. (See Interpreting the AQI.)| 2025 -- Sorted by Maximum Value | ||||||||
|---|---|---|---|---|---|---|---|---|
| Location | Region | CAMS | AQS | Date | Time | Value | POC | Hours Exceeded |
| Galveston 99th St. C1034/A320/X183 | 12 | 1034 | 48_167_1034 | February 1 2025 | 15:00 | 133 | 1 | 1 |
| POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site. | ||||||||
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.
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.