Outback NSW bore the brunt of the state's hot weather on Thursday and relief is still days away, the Bureau of Meteorology says.
Bureau forecaster Olenka Duma says hinterland towns near the Queensland border sweltered through some of the state's hottest temperatures on Thursday.
"It's just gone up to 48.4 at Tibooburra, so it may climb in the next couple of hours, but I don't think it will break 49," she told AAP at 5pm (AEDT).
Bourke residents faced a high of 46.8C.
"It's still going to be hot tomorrow up in that area," Ms Duma said.
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"Saturday is when the temperatures will start to see a good 10 to 15-degree drop."
In inner Sydney a cool change swept through mid-afternoon, bringing the mercury at Observatory Hill down from 34.5C at 3pm (AEDT) to 28.9C by 3.30pm (AEDT).
Sydneysiders seeking respite at the Wet'n'Wild water park in the city's west about lunchtime instead found themselves sweltering in heavy traffic, the Transport Management Centre said.
The car park at the water park was full by 1pm (AEDT).
By early evening some holidaymakers were still experiencing lengthy traffic snarls.
Along the Pacific Highway between Woolgoolga and Emerald Beach, southbound motorists were queued for five kilometres before 6pm (AEDT).
Despite a feared spike in accidents at the state's beaches and backyard pools, paramedics said people had heeded warnings to look out for children near the water and to avoid drinking before taking a dip.
A NSW Ambulance Service spokesman told AAP there were no drownings or near-drownings.
"But we do suffer a spike in heat-related jobs on days like this," he said.
