Newcastle, Lake Macquarie, Maitland, Cessnock, Williamtown, Tocal, Singleton and Scone hit temperatures above 40 degrees on Sunday.

Cessnock recorded the region's highest temperature of 41.9 degrees at about 4.30pm.

Nobbys hit a high of 40.1 degrees at 3.30pm.

The Bureau of Meteorology's senior climatologist Agata Imielska said NSW had experienced a "severe heatwave".

Bureau meteorologist Hugh McDowell said the minimum monthly temperature record for November was broken at Nobbys at 5.30am on Sunday.

"The minimum overnight for Nobbys was 24.1 degrees. The previous record was 23.1 degrees on November 3, 2018," Mr McDowell said.

The Nobbys weather station had been "recording for 64 years".

"So that's a pretty decent record," he said.

The bureau issued a severe weather warning for damaging winds in parts of the Hunter on Sunday. Gusts of up to 85 kilometres were recorded at Nobbys, but the worst didn't eventuate.

A NSW State Emergency Service spokesman said there was "nothing major" in the Hunter. The SES did have 17 jobs in Newcastle, with incidents such as trees and power lines down.

Hunter Surf Life Saving branch president Henry Scruton said suspected spinal injuries occurred with a female at Redhead on Saturday and at the northern end of Nobbys on Sunday when a male "hit the sand bank".

"Both were taken to John Hunter Hospital," he said.

The Hunter faced a "severe fire danger" on Sunday, with a total fire ban in effect. While more than 45 bush and grass fires were burning across NSW on Sunday, the Hunter was largely unscathed.

NSW Emergency Services Minister David Elliott warned the public to expect more severe weather "over the course of this fire season".

"The community unfortunately thinks that, after last season, we are not at risk of bushfires. Ninety per cent of the land mass across NSW is potentially exposed to the sort of bushfire threat we saw last year," Mr Elliott said.

The Nobbys temperature record was among 12 minimum monthly records broken across the state on Sunday morning.

Six monthly maximum temperatures were also broken on Saturday.

Three areas - Camden, Bankstown and Horsley Park - broke their minimum annual records.

"That was their hottest minimum temperature ever," Mr McDowell said.

Mr McDowell said hot, dry air had formed in central Australia before moving "across the state on north-westerly winds".

"With long-term trends, increasing temperatures have been directly attributed to climate change," he said.

NSW Ambulance reported its third busiest day on record on Saturday. It deployed additional resources across the weekend, as cases of heatstroke rose.