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Eight-Hour Ozone High Value Days for 2020
as of September 30

The table below lists the daily maximum eight-hour ozone concentrations measured which meet or exceed 71 parts per billion in 2020 in each community where the DAQ 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
2020 Sorted by Maximum Value
LocationRegionCAMSAQSDateTimeValuePOC
Walter Johnson 1 7132_003_0071August 3 202010:00821
Walter Johnson 1 7132_003_0071August 18 202009:00821
Joe Neal 1 7532_003_0075August 3 202010:00811
Paul Meyer 1 4332_003_0043August 18 202009:00791
Paul Meyer 1 4332_003_0043August 3 202010:00781
Walter Johnson 1 7132_003_0071May 6 202010:00781
Joe Neal 1 7532_003_0075June 22 202009:00781
Joe Neal 1 7532_003_0075July 9 202008:00781
Joe Neal 1 7532_003_0075August 18 202010:00781
Indian Springs 1 777232_003_7772July 9 202009:00781
Paul Meyer 1 4332_003_0043May 6 202011:00771
Paul Meyer 1 4332_003_0043July 9 202008:00771
Walter Johnson 1 7132_003_0071July 9 202008:00771
Apex 1 2232_003_0022May 6 202011:00761
Paul Meyer 1 4332_003_0043May 28 202009:00761
Joe Neal 1 7532_003_0075May 6 202011:00761
Green Valley 1 29832_003_0298July 9 202008:00761
Walter Johnson 1 7132_003_0071September 2 202011:00751
Joe Neal 1 7532_003_0075September 26 202010:00751
Jean 1 101932_003_1019May 6 202009:00751
Paul Meyer 1 4332_003_0043May 9 202011:00741
Paul Meyer 1 4332_003_0043June 22 202008:00741
Paul Meyer 1 4332_003_0043August 19 202009:00741
Walter Johnson 1 7132_003_0071August 19 202009:00741
Paul Meyer 1 4332_003_0043June 26 202010:00731
Paul Meyer 1 4332_003_0043September 2 202011:00731
Walter Johnson 1 7132_003_0071June 22 202008:00731
Joe Neal 1 7532_003_0075August 19 202010:00731
Jerome Mack 1 54032_003_0540May 6 202010:00731
Jean 1 101932_003_1019July 9 202007:00731
Jean 1 101932_003_1019August 3 202010:00731
Paul Meyer 1 4332_003_0043July 8 202012:00721
Joe Neal 1 7532_003_0075August 7 202010:00721
Green Valley 1 29832_003_0298May 6 202011:00721
Green Valley 1 29832_003_0298August 3 202010:00721
Jerome Mack 1 54032_003_0540July 9 202008:00721
Boulder City 1 60132_003_0601August 3 202011:00721
Indian Springs 1 777232_003_7772August 7 202011:00721
Paul Meyer 1 4332_003_0043August 21 202009:00711
Walter Johnson 1 7132_003_0071May 9 202011:00711
Walter Johnson 1 7132_003_0071May 28 202009:00711
Walter Johnson 1 7132_003_0071July 8 202012:00711
Walter Johnson 1 7132_003_0071August 7 202009:00711
Walter Johnson 1 7132_003_0071September 26 202009:00711
Joe Neal 1 7532_003_0075August 20 202010:00711
Green Valley 1 29832_003_0298August 19 202009:00711
Boulder City 1 60132_003_0601July 9 202010:00711
Indian Springs 1 777232_003_7772August 3 202011:00711
POC (Parameter Occurrence Code): a code used to correctly separate data from multiple instruments at one site.

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 0.201 - 0.2011
401 - 500 0.505 - 0.604 Not Defined
500+ Not Defined Not Defined

PLEASE NOTE: This data has not been verified by the Clark County Department of Air Quality 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 Clark County Department of Air Quality 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.