A smoke alert is active for areas between Two Rocks and Mandurah and the Perth hills.
The smoke is a result of prescribed burns being carried out and is expected to clear by tomorrow afternoon.
The Parks and Wildlife Service is planning two large prescribed burns in the Perth hills area over the coming days, which may produce further smoke over the metropolitan area. These 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.
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, and those with conditions exacerbated by smoke should take precautions in line with their medical advice for these circumstances.