Thunderstorm, flood warnings issued for NSW, Queensland, Victoria

On the NSW South Coast rainfall totals above 300 mm are possible as storms unleash a deluge on small towns.

In 24 hours Sassafras has recorded 231 mm, while 196 mm has fallen at Ulladulla and 225 mm at Jervis Bay airfield.

The Bureau of Meteorology's Angus Hines said the Illawarra and South Coast had copped the brunt of the rain so far.

"A number of weather stations have recorded over 150 mm of rain since 9am Tuesday and some stations are up over 200 mm - this is enough rain to cause surface and flash flooding," he said.

"Another 100 mm of rain could fall today - bringing two-day rainfall totals up in excess of 300 mm."

He said the rain combined with damaging wind could bring down trees and possibly cause power outages.

Severe thunderstorm warnings are current for large parts of NSW and the ACT on November 29, with heavy rain, large hail and damaging winds.

"An upper-level low over western NSW is maintaining unstable conditions across large parts of the state today," the Bureau said.

Intense rainfall could lead to "dangerous and life-threatening flash flooding" in parts of the NSW South Coast, along with damaging winds.

For northern NSW and south-east Queensland there is also the threat of supercell thunderstorms, which can last for several hours.

"This allows supercell thunderstorms to intensify more than regular storms, and they can bring even more dangerous severe weather - heavy to intense rain, damaging or destructive winds and large into giant sized hail," Mr Hines said.

Earlier on November 29 the SES carried out two flood rescues - two people from a car at South Nowra, and people at a home in Wrights Beach.

It was among more than 200 incident call outs in NSW in the 24 hours to 9am.

NSW SES is urging people to assess conditions before traveling on the roads, not to walk, ride or drive through flood waters and to heed any warnings.

The storm risk continues for south-east NSW, eastern Victoria, parts of interior South Australia and the Northern Territory on November 30.

"The Gippsland area becomes the focus of the heaviest rainfall for [November 30]... we will expect over 100 mm of rain to fall, particularly east of Bairnsdale," Mr Hines said.

"Flooding impacts are likely here too."

He said some areas in northern Victoria would receive in excess of a month's worth of rainfall during November 29 and following days.

Swan Hill on Victoria's northern border with NSW recorded 85 mm in 24 hours.

An initial flood watch is in place for Gippsland and parts of north-east and south-west Victoria.

By the weekend the storm risk will be more subdued and seasonal in parts of the northern Queensland and northern NSW coasts, Mr Hines said.

It comes after South Australia was lashed with storms on November 28, causing thousands to lose power and flights grounded at Adelaide Airport.

Keep updated with weather warnings at bom.gov.au/australia/warnings