Arizona Air Quality Information

Hotter temperatures don't mean higher ozone


Since last Wednesday (7/10), the high temperature at Sky Harbor has reached 110°F or higher every day, expect for the 14th. And today is forecast to see a high of 114°F. But what about ozone? On three of those days, ozone reached an Air Quality Index (AQI) of 100 or 101, at or just above the federal health standard. However, on two of those days, ozone only reached an AQI of 67 and 77. And ozone is only forecast to reach an AQI of 84 today (the AQI is the maximum 8-hr average of the day).

Some might assume that, when temperatures are hotter, ozone levels should therefore be higher. But this is not always true. Though ozone levels are often high when temperatures are hot, this is more a result of the atmosphere being favorable for ozone formation and accumulation via light winds and clear skies, not hot temperatures. Additionally, other factors can come into play, such as winds. Winds helped to limit ozone to an AQI of 67 and 77 two days last week, and they're the reason why ozone is only forecast to reach 84 today.

It should also be noted that the two highest ozone AQI days so far this year--June 8 and 24--which saw an ozone AQI of 133 and 136, respectively, saw high temperatures of 100°F and 103°F. So, this year's highest ozone levels weren't even associated with temperatures above 110°F, or 105°F, for that matter.

To know forecast ozone levels, view the Phoenix 5-Day Air Quality Forecast HERE.