Sydney’s summery public holiday weather set to turn chilly, with more than 10C drop in temperature coming

Sydney's clear skies and 30C temperatures are forecast to give way to a dramatic cool change, with hailstorms possible in New South Wales' north.

On Monday afternoon the highest temperature in the Sydney metro area was 30.8C, recorded at the airport. The state high was 33.5C in Moree.

A cold front was expected to sweep into the region late on Monday evening, bringing with it showers, overcast skies and a high of about 19C on Tuesday, the Bureau of Meteorology's Jiwon Park said.

's breaking news email

"There may a significant change of weather pattern, especially across eastern NSW, from warm and dry conditions to wet and relatively cool conditions in the wake of southerly changes expected this evening into tomorrow," Park said.

Cooling behind the change will see 8C to 12C degree temperature drops across the state, he said.

On Tuesday afternoon, the cold front is expected to reach northern NSW, where it will interact with a trough of low pressure extending from eastern Queensland , heightening the risk of thunderstorms.

"We may see a development of severe thunderstorms about the northern rivers and mid-north coast regions, where we may see damaging wind gusts exceeding 90km per hour, and localised heavy [rain] and large hail," he said.

As the southerly travels north, Brisbane's high of 33C on Tuesday is forecast to drop to about 24C on Wednesday.

Park said temperature fluctuations were normal in spring and the warm public holiday observations were a way off Sydney metro's October record of 38C.

"During the spring season, we expect temperatures to fluctuate from warmer than seasonal averages down to cooler than seasonal averages because of the competition between the heat and the cold fronts, and the unstable weather patterns because of that," he said.

Two more cold fronts will come on the heels of Monday evening's southerly change, with a week of changeable temperatures ahead for the Sydney region, Park said.

A small bushfire near Oberon was burning out of control on Monday afternoon. It was expected to be brought under control, a Rural Fire Service spokesperson said.

The Sydney area, Illawarra and Shoalhaven were the only high fire danger areas in the state on Monday. Those areas were expected to return to moderate danger on Tuesday.