A SMOKE alert has been issued for the thick haze which has blanketed the Perth metropolitan area overnight.
The Parks and Wildlife Service at the Department of Biodiversity, Conservation and Attractions issued the alert for the area between Two Rocks, Rockingham and the Perth Hills.
The haze is a result of a prescribed burn conducted yesterday afternoon.
The Department of Fire and Emergency Services (DFES) has advised people to shut doors and windows and turn off air-conditioners if the smoke is particularly thick near them.
They reminded people smoke may reduce visibility on some roads and urged motorists to turn on headlights and travel at appropriate speeds.
DFES also urged people with conditions which may be exacerbated by smoke, such as asthma and pre-existing respiratory or cardiovascular illnesses, to take precautions in line with their medical advice.