The Department of Parks and Wildlife has issued a smoke alert for Mandurah and the Perth metropolitan area.
The smoke is from prescribed burns being carried out today 20 kilometres south-east of Mundaring and eight kilometres south-south-east of Dwellingup.
The smoke is expected to accumulate overnight and clear during tomorrow.
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.
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.