A bushfire emergency has forced the evacuation of a town in Perth's south as the city posts its earliest 40-degree day in December on record.
The temperature climbed to 41.6 degrees Celsius just after midday, eclipsing the previous record of 40.4C on December 5, 1977.
Perth's sweltering start to summer comes on the heels of a record-breaking November.
"We've got a slow-moving high pressure system sitting in the bight and it's directing very hot north-easterly air down towards the west coast," Bureau of Meteorology spokesman Neil Bennett said.
"And it won't just be Perth; right up and down the west coast we're going to see some very hot temperatures over the next few days."
Temperatures are forecast to far exceed Perth's December average of 29.1C for the rest of the working week.
Bushfire threatens lives and homes in Perth's south
Meanwhile, about 100 firefighters are battling a bushfire close to the town of Forrestdale in Perth's south-east.
An emergency warning has been issued for the blaze, which is threatening lives and homes in an area bounded by Armadale Road, Tonkin Highway, Oxley Road, Commercial Road and Weld Street.
Residents in the immediate area have been told to evacuate if the way is clear and, if not, to shelter in their homes in a room with two exits away from the fire front.
A temporary evacuation centre has been established at the Armadale Arena.
The fire has burnt through 20 hectares of bushland and is moving fast in a north-easterly direction towards the edge of the town.
Department of Fire and Emergency Services spokesman Will Blackshaw said the heat and wind was proving a challenge for firefighters.
"It's a bit breezy at the moment — the weather conditions is the big thing the firefighters have against them at the moment."
He said firefighters were working hard to protect properties, including Forrestdale Primary School.
Forrest Road and Broome Street have been closed to traffic.
Another hot blast before some weekend relief
Maximum temperatures above 35C are forecast each day until a milder change comes through on Saturday, when a trough that is hovering along the west coast moves inland, allowing cooler onshore winds to push through.
Friday is also expected to surpass the 40C mark, putting Perth on track to record its hottest first week of December since records began in 1897.
"There will be a little bit of relief for the west coast on Wednesday as a trough moves inland but it's not going to bring much relief because the trough will then push back offshore on Thursday and the heat will return with a vengeance," Mr Bennett said.
"It could be even hotter than today on Friday. It will depend very much on the timing of the sea breeze as to what the temperatures could get to."
Reprieve will come in the form of a cold front on Saturday which will see Perth's maximum drop into the high 20s.
"On Saturday there's a frontal system approaching from the south-west and that will really push cooler air in and we'll see a drop in temperatures," Mr Bennett said.
Perth's blistering start to summer comes on the back of a very warm November, which saw the city notch up a mean maximum temperature 2.4C above average.
It also smashed its record for the hottest ever November day when it hit 40.4C on November 16.