If you’ve stepped outside this week, you may have noticed more haze than usual. That is pollution from smoke, tailpipes and power plants.

Lower temperatures and the holidays play a role.

Maricopa County issued a no burn day on Monday due to unhealthy levels of fine particulate matter. 

During winter, cold air temperatures generally keep fine particulates in lower elevations, which means pollution from smoke and car exhaust settles closer to the ground.

Pollution levels increase over the weekends and holidays as people light fires.  

Arizona Department of Environmental Quality meteorologist Matt Pace says this Christmas will be no different. 

“Try to reduce the amount of pollution you’re using, instead of lighting that fireplace, try to convert it to gas or electric. But if you do have to use a fireplace, make sure your wood is dry,” Pace said. 

Wet wood produces more pollution as more smoke is emitted.