Perth has registered a record sixth consecutive day over 40C as the heatwave in Western Australia continued on Sunday ahead of an expected cool change on Monday.
Perth reached 40.1C about midday on Sunday, marking the 11th day above 40C this summer.
Perth’s previous record for total summer days over 40C was seven days in 2015-16.
When Perth reached 40C on Friday for a fourth consecutive day it matched the previous record sequence reached in the WA capital on three previous occasions, including last Christmas.
Luke Huntington, duty forecaster at the Bureau of Meteorology in WA, said it had been “particularly hot all along the west coast” with Geraldton recording five days over 43C from Tuesday and Carnarvon reaching 45C.
Huntington told Guardian Australia there was “definitely a cool change coming through for tomorrow, we’re back down to 33C [in Perth] tomorrow”.
“It looks like cooler temperatures throughout the week, around the low 30s, but it looks like the heat returns next weekend, with tops near 40 again.”
“Perth’s summer [heatwaves] are typically caused by a heat trough, which usually forms down the west coast, and when it’s offshore it brings down the hot hair through inland parts, then when it moves inland it brings cooler sea breezes.
“What’s unusual about this event is the trough has remained offshore for multiple days, bringing that hot air down.
“Normally we’d only see that trough hanging around for two or three days. For some reason, which we’re not too sure about yet, that trough has been hanging off the coast for at least four or five days.”
Last week a temperature of 50.7C was recorded at Onslow in WA’s Pilbara region, matching the hottest temperature ever recorded in Australia, according to the preliminary data.
Two other sites notched 50C-plus temperatures, a level only previously reported three times on standardised equipment.
On Friday, Robert Lawry, a senior hydrologist at the bureau’s WA office, said February is typically Perth’s hottest month.
The previous periods with seven 40C days in Perth between November and March came in 2006-07, 2015-16 and 2019-20, a tally already exceeded this summer.
“There’s a pretty obvious trend there,” Lawry said. “They’ve all happened in the last 20 years.”
The odds of enduring very hot temperatures have already increased substantially as a result of climate change, he said, adding, “this kind of thing is what you can expect to happen more frequently”.
The bureau’s forecast for the Victorian capital is for a week of days reaching 30C or more. Sydney, though, is in for a continuation of its mostly muggy and damp days, with humidity levels well above the norm for January.