Rockingham, Mandurah and surrounding areas were blanketed by smoke overnight.
The smoke was due to prescribed burns being carried out by the Parks and Wildlife Service.
A smoke alert was issued for Busselton, Donnybrook, Bunbury, Mandurah and the Perth metropolitan area on Tuesday night.
The smoke is expected to clear this morning.
WHAT TO DO:
• 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.
West Aussies urged to be on high alert after surge in winter house fires
New $3.4 million boardwalk to be constructed at Lake Clifton thrombolites
City of Mandurah rolls out new tactile bin lids, accessibility stickers to support residents with low vision
Driver dies in hospital after Australind crash
Welfare concerns for woman with dementia last seen in Cooloongup
Charges laid over fatal West Coolup crash
Final boiler comes crashing down at old Kwinana Power Station
Kwinana Police seek public's help to find wanted man
Police continue to investigate assault during Rockingham Christmas lights activation