Temperatures set to cool after Sydney endures sweltering night

Sydneysiders can soon breathe a sigh of relief as the weekend's heatwave will give way to milder spring days early in the next week.

After sweltering through record-breaking temperatures on Saturday night, Sydneysiders woke to another sizzler on Sunday - with the mercury heating up to 28 degrees by 6am.

Despite high cloud cover, the temperature has remained high throughout Sunday, reaching a maximum of 29.2 degrees in the CBD on Sunday afternoon - 9 degrees above September averages.

Meanwhile, regional areas of NSW faced a third consecutive day of sweltering temperatures.

Gosford notched 33 degrees, while Newcastle reached 33 degrees shortly before midday. On the North Coast, Port Macquarie, Coffs Harbour and Grafton all soared above 38 degrees.

Dry westerly winds have picked up across the state in the afternoon, reaching up to 60km/h at Sydney Airport and 57km/h at Richmond on Sunday afternoon.

While a total fire ban operated throughout the state from the Illawarra to the Queensland border, the dry north-westerly blusters wreaked havoc for the NSW Rural Fire Service.

Up to 100 bushfires burnt across NSW on Sunday evening, of which 29 were not contained, NSW RFS spokesman James Morris said.

Across the weekend, a total of 270 new fires blazed, with more than 1500 firefighters working to contain the fires, he said.

In one out-of-control fire at Innes View on the state's North Coast, structures have been destroyed, the NSW RFS said in a statement.

Some relief should be in store on Sunday night as a westerly is expected to move through Sydney gradually dropping night-time temperatures to about 15 degrees.

Yet Sydneysiders enjoying the first week of school holidays can expect another warm and sunny day on Monday, of 27 degrees, Craig McIntosh, meteorologist at Weatherzone, said.

Temperatures should gradually cool off for Tuesday, bringing in milder spring weather of 24 degrees.

"We'll see a wind direction change, as wind coming from the north-west will change to the south-west by Tuesday, bringing with it lower temperatures," he said.

"But it will still remain fairly warm ... and certainly warmer than average for September."

A total fire ban will remain in place for northern coastal regions of NSW on Monday, as firefighters continue to monitor conditions, Mr Morris said.

A weak rain band is expected to cross NSW on late Wednesday or Thursday morning.

"I'm sure the rain will be useful, particularly to farmers, but it doesn't look like it is going to be enough," Bureau of Meteorology senior meteorologist Jake Phillips said.

Temperatures around NSW this weekend have been warmer than record minimums usually experienced typically in the warmer months of October, November, March and April.

Much of NSW would have felt like they spooned a hot water bottle on Saturday night. Temperatures in Sydney did not dip below 26 degrees overnight, an event weather experts describe as "phenomenal".

"We expect lots of variability for this time of year, but not quite to these extremes," Mr Phillips said.

Saturday's minimum, of 23 degrees, recorded at 9am on Saturday, was a new record. The highest previously recorded minimum was 22 on September 4, 2003.

The heat comes just over a week after Sydney notched 33.8 degrees, the hottest day so early in the warming season, and not far shy of the record high for a September day of 34.6 degrees set in 1965.

This story Temperatures set to cool after Sydney endures sweltering night first appeared on The Sydney Morning Herald.