Environmental regulators have issued an ozone high pollution advisory for Saturday in metropolitan Phoenix.
The advisory was issued because the area's ozone levels are expected to exceed the federal health standard for air quality.
Regulators say people with respiratory problems should limit their outdoor activities, especially children and the elderly.
Also, people are encouraged to drive only when necessary or use public transit or carpool.
Other recommendations include making sure containers with household cleaners and other chemicals are sealed to prevent vapors from evaporating into the air.