Sydneysiders have sweltered as temperatures soared above 42C in parts of the city before an afternoon change caused the mercury to plummet more than 15C.
Edward Townsend-Medlock, a meteorologist at the Bureau of Meteorology, said a sea breeze followed by the cool change delivered the sharp drop on Tuesday.
Canterbury, in Sydney’s west, experienced one of the largest changes. It was 40.6C at 3pm, cooled to 35.5 with the seabreeze at 3.24pm, and then plummeted to 25C at 4pm when the cool change hit.
“So over a half an hour period, that’s a 10C drop, which is fairly significant,” he said, adding there had been a 15C shift within an hour.
He said a 15C change in an hour was significant, although southerly busters were known for bringing rapid cool changes.
The bureau said New South Wales bore the brunt of the pool of very hot air that sent temperatures in parts of South Australia and Victoria into the 40s on Monday.
Sydney’s main Observatory Hill weather station reached 36C by 1pm but after the cool change hit it dropped to 29C by 4pm. The temperature reached 42.5C at about 1.30pm at Sydney airport and plummeted to 24C by 3.50pm. It fell almost 10C between 3pm and 3.30pm.
Earlier, the temperature reached 43C at Badgerys Creek and Penrith and 42C at Bankstown, Holsworthy and Olympic Park. At Olympic Park, the temperature swiftly fell to 26C.
Severe heatwave warnings had been in place for large parts of NSW.
Dubbo, Parkes and Forbes all reached 41C on Tuesday. It was 42C in Girilambone, Trangie, Tibooburra and Brewon and 43C in Borrona Downs.
Hines said the southerly buster that caused the sudden drop in temperatures was likely to cause “showers and thunderstorms across NSW”.
A damaging wind warning was in place from Wollongong up to north of Gosford, with strong gusts upwards of 90km/h possible.
“Strong winds can have a lot of impact, including bringing branches and entire trees down, potentially leading to power outages, and it can make for difficult driving conditions, particularly in tall vehicles like caravans, as well as on motorbikes,” Hines said.
In Victoria, the state’s emergency warning service, VicEmergency, issued a number of alerts to communities in the west due to out-of-control bushfires.
Authorities advised people in Victoria Range in the Grampians National Park from Bullawin Road to Billywing Road, Goat Track area to leave immediately, and several other communities were advised to monitor changing conditions.
On the other side of the country, heatwave conditions experienced last week were rebounding, with temperatures forecast to be 4C to 12C warmer than the typical January averages across western parts of Western Australia – and up into the 40s over the next couple of days.
While some states were enjoying milder conditions on Tuesday, northern Queensland could expect persistent wet weather to continue throughout the week, with the heaviest and most persistent falls expected between Cooktown and Ayr.
Later in the week and into the weekend, Queensland could see its first tropical cyclone this summer, Bradbury said. A low pressure system forming over the Coral Sea and Gulf of Carpentaria posed a low-to-moderate chance of becoming a tropical cyclone.
Australia’s land surface has warmed by 1.5C since 1910, according to the BoM, with the climate crisis making heatwaves longer and more intense, and increasing the number of extremely hot days.
