NSW residents are set for a weekend of wild weather with heat, fire danger, snow, and thunderstorms all forecast over the next two days.

"It's quite a mixed bag," Bureau of Meteorology forecaster David Wilkie said.

"There's a lot of weather happening and depending where you are you'll get a different slice of it."

Ahead of a strong cold front, Saturday is expected to bring above-average temperatures to the north and east of the state, reaching the high 20s and 30s.

Sydney is forecast to hit 31 on Saturday in a "windy, mostly sunny day", and a total fire ban has been declared for much of the state.

"We're looking at temperatures between 8-10 degrees above average for a broad area," Mr Wilkie said.

The Illawarra region and the alps will face strong and potentially damaging wind, with possible severe thunderstorms and lightning in northern parts of NSW.

There will be wind warnings in place along much of the state's coast line.

This was the scene at Bondi Beach in mid-August, when the temperature hit 26 degrees in winter ( ABC News )

Rainfall was below average over winter, particularly in New South Wales, where it was the eighth-driest winter on record and the driest since 2002.

The strong winds and soaring temperatures will create the conditions for bushfires, and there are severe fire danger warnings in place for parts of the Hunter, Sydney, Illawarra, North-Western and Shoalhaven regions.

As the cold front sweeps through, Sunday will see a major drop in temperatures below 20 degrees Celsius — "around 5 degrees below average for this time of year", according to Mr Wilkie.

From the heat and fire dangers of Saturday, Sunday is set to see snow in the southern ranges above 700 metres, and hail.

Weather forecaster David Wilkie said the change in seasons could be one reason for the wild weather.

"Spring's the time we see this kind of abrupt weather changes," he said.

While the warm weather is set to please beach-goers and the snow will be good for those hitting the slopes, the forecast might not be welcomed by farmers still affected by drought.

"We're going to see almost every kind of weather that we can list except for, unfortunately, rainfall," Mr Wilkie said.