It was a tale of two cities for Sydney on Friday.
The city went from sweltering in record-breaking highs of over 45C to below-average temperatures in the space of about 10 minutes on Friday night.
And while the cool change wiped out the sizzle, it also brought severe thunderstorms and damaging winds that had residents battening down the hatches.
Wind gusts of up to 100km/h swept through the city as temperatures dropped by about 10 degrees in 10 minutes from about 8pm (AEDT), Bureau of Meteorology (BoM) forecaster Jake Phillips said.
"It went from the mid-30s to mid-20s in the space of five to 10 minutes in most areas," Mr Phillips told AAP.
The plummeting temperatures brought some relief to Sydneysiders after a sweltering day which saw the mercury hit a record-breaking 45.8C at Sydney's Observatory Hill at 2.55pm.
The previous record of 45.3C was set on January 14, 1939.
The sizzling heat caused chaos across the city, with scores of heat-related illnesses, transport meltdowns and even melting roads and ice rinks.
By 5pm (AEDT) on Friday, the Ambulance Service of NSW had responded to 93 cases of heat exposure.
On top of that, 133 people fainted and 37 people were treated for vomiting, with most of those cases attributed to the heat.
Sparks from Sydney's monorail briefly set fire to trees and grass near the entertainment centre, while at the Big Day Out music festival in Homebush a St Johns Ambulance spokesman said the organisation treated 200 people, mostly for dehydration.
In western Sydney at the Australia Youth Olympics, basketball, canoe and athletics events had to be cancelled or postponed because of the soaring temperatures.
Meanwhile, most trains across the CityRail network were delayed by at least an hour on Friday evening, with overhead wiring and signal problems failing to cope with the extreme heat.
It was so hot in Sydney's northwest that a 20km section of Bells Line of Road started to melt, with authorities cutting the speed limit to 60km/h because of safety fears.
And the manager of Canterbury ice rink, in Sydney's southwest, said it was so hot the ice inside the rink had been melting all day.
By 10pmhowever, Sydney was at a comfortable 23 degrees and the severe thunderstorm warning was removed.
The worst gusts were recorded at Terrey Hills in northern Sydney about 5pm on Friday, with gusts of 104km/h recorded.
The State Emergency Service (SES) received about 100 calls for help, mostly to do with falling trees and roof damage, a spokeswoman said.
The cool weather is expected to continue on Saturday, with forecast highs of 25 in the city and 28 in the west.
"That is actually below average for this time of year," Mr Phillips said.
"It will be a vastly different day from what we saw (on Friday), but after today I don't suppose too many people will be complaining."