A cool southerly change is sweeping up the NSW coast after the state endured a summer scorcher, with temperatures climbing into the mid-40s.
Residents were urged to check on vulnerable friends and neighbours on Saturday as much of NSW sweated it out under a dome of heat that had spread across the continent from the west in recent days.
Temperatures in Penrith and Richmond in Sydney's outer west climbed to 43C in the late afternoon, with Badgerys Creek hitting 44C just after 4pm - the highest temperature recorded in the city.
The heat was widespread across the state, with the central and lower western districts also enduring extreme conditions and temperatures.
Forbes and Condobolin in NSW's Central West both reached 44C.
The weather bureau issued a severe weather warning for the metropolitan and Illawarra districts late on Saturday as the cool change arrived.
"A southerly buster may produce damaging winds over parts of the Sydney and Illawarra coasts," the warning read.
Winds of 70km/h were expected to reach the CBD on Saturday evening, with potential gusts of up to 90km/h.
A warning for severe thunderstorms threatening large hail and damaging winds is also in place for the Hunter, South Coast, Snowy Mountains and Mid-North Coast forecast districts.
"Storms are moving to the east and southeast towards the coast," the bureau warned.
Heatwave warnings remain in place for all mainland states, with high to catastrophic fire danger alerts issued for sections of South Australia, northern Victoria, outback NSW and Greater Sydney.
The cool change had already brought relief to southern states overnight, with Adelaide reaching a maximum 17C and recording more than 20mm of rain since 9am on Saturday.
About 35,000 households in South Australia lost power on Friday due to catastrophic bushfire risk, dry lightning and strong winds.
SA Power Networks said it had to disconnect about one-third of those customers due to fire risks, with all but 1400 reconnected to the grid by Saturday morning.
The NSW Rural Fire Service issued total fire bans for five state districts including Sydney, with several dozen fires burning but none out of control.
The heat promoted warnings to 100,000 music fans heading to Sydney's Olympic Park precinct to attend concerts by the Foo Fighters and 50 cent and the EPIK indoor music festival.
Authorities urged concertgoers to allow extra time to travel in the heat and seek out shade while waiting for transport.
A top of 27C is forecast for Sydney on Sunday.
