A smoke alert has been issued for areas ranging from Dawesville to Myalup.
The Parks and Wildlife Service issued the alert at 2.50pm Friday, saying the smoke it the result of a prescribed burn and is expected to clear overnight.
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 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.
Visit emergency.wa.gov.au to stay up to date.