A second uncontrolled blaze was being fought in nearby Yallingup, south of Margaret River. Residents on the eastern side of Caves Road were being urged to evacuate with emergency warnings still in place on Thursday night.
The Fire and Emergency Services commissioner, Darren Klemm, said the fire was spreading fast in multiple directions with hot, dry and windy conditions expected to continue into the evening.
The warning area had expanded significantly since an emergency alert was first issued on Wednesday. More than 100 firefighters were battling to strengthen containment lines.
Emergency WA issued a warning to avoid non-essential travel to the area, with visibility limited due to smoke. Motorists were urged to take extreme care and drive to conditions.
Farming properties on the eastern side of Caves Road were of particular concern as a trough passed through the area from the coast.
An evacuation centre had opened at Margaret River Recreation Centre, with a second centre opened at Geographe Leisure Centre on Thursday evening. A community meeting was held at 6pm on Thursday at Margaret River Heart.
Klemm said the cause of the fire was yet to be determined, playing down the presence of police arson squad officers in the area. He said anyone planning to travel to the Margaret River region from Perth should reconsider their plans.
Wednesday was the hottest night for Perth in seven years, dropping to just 26.8C at 5.30am.
Easterly winds were continuing on Thursday but the outlook for next week was cooler in the capital city.
Earlier today, the WA premier, Mark McGowan, urged residents to follow official updates on the blaze.
A large aerial tanker was being deployed and another was expected to arrive from New South Wales.
The bushfire started near the intersection of Caves Road and Calgardup Road in Boranup, almost 300km south of Perth.
Hot and windy conditions had made life difficult for firefighters with the temperature reaching the mid-30s across the south-west on Thursday.
The fire was travelling fast in a south-westerly direction and aerial support had been sent to assist ground crews.
Klemm said the Yallingup bushfire had originated at a house which was believed to have sustained some damage.
Two watch and act warnings were also issued for parts of Redgate, Witchcliffe, Forest Grove, Karridale, Kudardup, Deepdene and Hamelin Bay, east of Caves Road between Spencer Road and Johnson Road and areas near the coastline between Injidup beach car park and Moses Rock Road.
