Friday will be the eighth day this year the Valley’s been under a high pollution warning. Continued high temperatures could lead to more ozone advisories through the weekend. 

All week, the Phoenix area has been under either an ozone watch or warning. Tuesday’s ozone levels were some of the highest all year. Very hot temperatures and winds from the east have led to a buildup of the dangerous invisible gas, which leads to respiratory problems, especially for the very old and very young.

Eric Massey at the Arizona Department of Environmental Quality said ozone buildup is often cyclical – sometimes we have good years, sometimes bad years. So far, 2012 hasn’t been so good. And there might be more pollution advisories on the way.

“My forecasters are pretty concerned about concentrations coming up for this weekend, given all of the heat," Massey said. "Typically, September is a pretty clean month for us here in Phoenix, so we’re not too worried once we get out toward September, though it’s something we’ll continue to watch. But it’s really hard to predict exactly how many, or how bad it could be, through the end of August."

The Phoenix area is also under an excessive heat warning through the weekend, with forecast highs consistently above 110 degrees.