Four homes have been lost near Denmark on the south coast, while the damage is not yet known from two emergency-level bushfires in the eastern Wheatbelt and southwest town of Bridgetown.
The fire in the Wheatbelt has burned through about 40,000 hectares and at one point spanned 35 kilometres long.
An emergency warning remains in place for the shires of Quairading, Bruce Rock, Corrigin, Kondinin and Kulin, with residents advised it is too late to leave.
"Leaving now would be deadly," the Department of Fire and Emergency Services said on Monday.
"You need to shelter in your home in a room away from the fire front and make sure you can easily escape."
Those in surrounding areas have been told to get out now if they can, or else make their final preparations to actively defend their property by monitoring for spot fires.
DFES commissioner Darren Klemm said the Wheatbelt fire was the greatest concern for authorities because of the open terrain.
With Perth having sweltered through its hottest January on record and the Pilbara town of Onslow surpassing 50C to equal the nation's highest temperature, Mr Klemm said there was no doubt climate change was intensifying bushfire conditions.
He said the fire near Denmark had doubled in size overnight on Friday night.
"That's just not normal, and I think the thing for people to understand is the intensity of these fires and the activity at night are two real pointers towards things are changing," Mr Klemm told Perth radio 6PR.
"We're seeing things that we haven't seen very often."
A damage assessment for the Bridgetown fire is expected to be completed on Monday after four homes were lost near Denmark.
Another fire near the Wheatbelt town of Narrogin was also at emergency level but has since been downgraded to watch and act.
Mr Klemm said there were reports of a "pretty significant impact" to large numbers of cattle as well as a piggery east of Narrogin.
An emergency warning remained in place on Monday for parts of Bridgetown and surrounding areas including the small railway town of Hester.
All residents within 500 metres of Timber Treaters in Hester were urged to relocate immediately on Sunday night due to toxic materials being dispersed by the wind.
"Although Hester is no longer under direct threat from bushfire, it remains in the emergency area and care must continue to be exercised," the DFES said.
About 40 firefighters are battling the blaze, which is contained and has burnt out more than 2200 hectares.
Western Power on Monday said it was working to restore power to about 13,800 customers across the network, most of whom were in the metropolitan region.
About 600 homes in Bridgetown and 400 in Denmark remain without power.
10°C