Temperatures are dropping across NSW after a day of record highs contributed to catastrophic fire danger and more than 80 blazes.

A southerly change moved across the north of the state on Sunday night bringing cooler temperatures but also the danger of increased winds and erratic fire behaviour in the short term.

Before the change a number of towns recorded their hottest ever day.

Port Macquarie hit 46.5 compared with a previous top of 43.3C, while in Kempsey it was 46.4C where the existing record had been 43.9C.

Taree reached 45.7C on Sunday, beating the previous highest temperature of 43C.

Walgett was the hottest town in NSW with the mercury hitting 47.9C.

Sydney got the change late on Saturday night so only reached 32C on Sunday. Out west in Penrith it was 38C on Sunday.

Bureau of Meteorology senior forecaster Neil Fraser said while the southerly change could bring damaging winds "the good news is it should be all easing off by the early hours of Monday".

The bureau isn't expecting storms overnight and the only lightning on Sunday evening was right over the Sir Ivan fire in central western NSW.

"It actually generated it's own thunderstorm cell over the top of the fire just after the change went through," Mr Fraser said.

Fire danger will remain very high on Monday in the Greater Hunter, Central Ranges, Northern Slopes, North Western and Upper and Lower Central West Plains fire areas.

But in welcome news for firefighters no part of the state is rated severe, extreme or catastrophic.

"The ratings are dropping away with the cooler air coming across," Mr Fraser said.

"The only part of the state still in the 30s (on Monday) is the northern inland areas."

There'll be a total fire ban in the North Western fire area only.