Environmental regulators have issued a high pollution advisory Thursday for metro Phoenix.
The advisory was issued in anticipation of light winds that could raise ozone levels.
Elevated ozone levels are expected in the coming days, too.
The aim of the advisory is to reduce pollutants at a time when the area's pollution levels may exceed the federal health standard for air quality.
Regulators say people with respiratory problems should limit their outdoor activities on Thursday.
Other recommendations include driving as little as possible and making sure that containers with household cleaners and other chemicals are sealed to prevent vapors from evaporating into the air.