Extract from ABC News
Perth has broken its record for the longest stretch of days over 40 degrees Celsius, as it swelters through one of its hottest summers on record.
Key points:
- Perth has notched up its 10th day over 40C this summer — a new record
- Five of those to date have been consecutive days — also a record
- The maximum temperature is expected to reach 38C on Sunday
At 1:10pm on Saturday, the temperature reached 40.1 degrees for the fifth day in a row, breaking the previous record of four days.
That had been set three times in history: between December 25 and 28 last year, in February 2016 and February 1933.
But duty forecaster Jessica Lingard said with a 39-degree maximum forecast for Sunday, it was unlikely the record would be broken again.
"There is a slim chance, but we have all got our fingers crossed that it's a little bit cooler," she said.
Ms Lingard explained the hot weather had been caused by a west-coast trough, a fairly common feature of summer in Perth.
"It develops down the west coast and when it sits offshore it causes north-easterly winds to bring down hot, dry air from inland and northern parts of WA, down the west coast and down into the south-west," she said.
"What we've seen over the last couple of months is these west-coast troughs lingering about the coast for several days, whereas in a normal season we might expect them to develop, only linger for a day or two."
Relief in sight
Thankfully, that system should bring cooler temperatures as it moves onshore.
That is expected to happen on Sunday, with temperatures in the low 30s forecast from Monday, including 31C on Australia Day.
Little over halfway through summer, Perth has also broken the record for the highest number of days over 40C between December and February.
So far, 10 days have broken that mark this summer.
The previous record was seven days, set over summer in 2015/16.
Even looking at a longer period between November and March, only seven days were hotter than 40C across 2006/7 and 2019/20.
On average, December only has one day over 40C, while February has 1.2.
Relief may be short-lived
Ms Lingard said we could expect this summer's numbers to climb.
"We do have another hot period forecast for next weekend, with temperatures increasing again," she said.
"This will not be the last hot period that we see for the summer period."
Ms Lingard said it was difficult to say why the systems were hanging around for longer, although there were some theories the bureau was considering, including weaker than usual synoptic patterns.
"We haven't had any tropical lows moving through or tropical cyclones moving through the Pilbara region, nothing to really flush out the heat in that area," she said.
But she said it was not possible to put the heat down to global warming at this stage.
"There are several factors involved that may not be specifically climate change-related," she said.
"This may just be a season where we don't get too many cyclones through the north-west, they all seem to be off the coast or in the eastern states.
"But if we look back to the State of the Climate report that the CSIRO and the Bureau wrote in collaboration in 2019, they discovered that there had been a warming of 1.4 degrees.
"If we take into account that background warming, these hotter temperatures are looking more likely."
Heat felt across the state
The particularly warm summer period has not been limited to Perth, with high temperatures recorded across the state.
Last week, the small beachside town of Onslow in the Pilbara equalled Australia's hottest day on record when the temperature peaked at 50.7C.
"We have seen extreme temperatures all the way down into the south-west around the Margaret River region," Ms Lingard said.
"We've also seen some very hot temperatures through Geraldton and up around Carnarvon and Coral Bay as well.
"Temperatures through western parts of the Pilbara and western parts of the Gascoyne have been quite extreme over the last couple of months, with temperatures in the mid to high 40s."
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