Prescribed burns south of Mandurah have created heavy smoke in the area.
A smoke alert has been issued between Two Rocks to Bunbury as result of prescribed burns.
The Parks and Wildlife Service is conducting two large prescribed burns in the Perth hills area over the coming days, which may produce further smoke over the metropolitan area.
The burns are located 25km south-east of Mundaring and 25km south-east of Dwellingup.
These burns have been identified as high priority, reducing fuel loads and assisting in protecting the towns of Mundaring, Sawyers Valley, Chidlow and Dwellingup.
Smoke is expected to clear by tomorrow afternoon.
If the smoke is particularly thick, it is recommended people shut doors and windows and turn off air-conditioners.
Smoke may reduce visibility on some roads and motorists should take care, turn on headlights and travel at appropriate speeds when travelling in these areas.
People with asthma and pre-existing respiratory or cardiovascular illnesses should follow their pre-prepared treatment plan.
People with conditions exacerbated by smoke should take precautions in line with their medical advice for these circumstances.