Maricopa County has exceeded the ozone standard 49 times just this year. It’s the most since 2012.

“We have only seen six good days for ozone since April 1,” said Matt Pace, who is with the Arizona Department of Environmental Quality.

He says the weather pattern of the monsoon season has kept pollutants sitting in the Valley, which then react with sunlight.

“We have just had high pressure sitting over us and you have calm winds during the day and we don’t get cloud cover, we don’t get the outflows soon enough to clear all that ozone out and then we exceed," Pace said.

Vehicles are the biggest contributors to high ozone levels in the metro area. Pace says the weather has shifted this week, though, and that’s improved the air quality.