Heavy rain may lead to flash flooding in parts of the New South Wales south coast today, a severe weather warning from the Bureau of Meteorology (BoM) says.

Motorists have been advised to avoid travel to the area, with up to 140 millimetres of rain expected to fall in some parts of the region.

Duty forecaster Dimitri Danchuk said there would be widespread rain all over south eastern coastal districts of the state.

“The most significant area will be on the south coast, around Moruya and Batemans Bay and nearby southern highlands roughly between Bowral and Braidwood,” Mr Danchuk said.

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“This rainfall is already happening, and was happening throughout the night; we have already accumulated 110 millimetres near Bega.

A fall of 100 millimetres was recorded in Batemans Bay, Moruya, the Clyde Mountain and the Brown Mountain over the past 24 hours.

“Heavy rains are possible all the way between Newcastle and Wollongong, including Sydney and all the way west to the Blue Mountains, Katoomba, Jenolan Caves and even the ACT and Canberra could see possible heavy rainfalls today.”

Mr Danchuk said Sydney’s Hills region saw rainfall between 50 and 70 millimetres over night.

He said he main culprit of the rainfall was a broad low pressure trough.

A warning on the bureau’s website said Moruya Heads, Araluen and Nerriga on the NSW south coast would also be affected by heavy rainfall.

“Since 9.00am yesterday, 110 millimetres fell at Bodalla Post Office and 108 millimetres at Mt Darragh on the south coast,” the statement said.

BoM forecaster Sean Carson said motorists should delay trips to the area because the rain may lead to dangerous driving conditions.

“If anyone was thinking of driving down the Clyde Mountain or the Brown Mountain today, my advice would be to delay that for a day or two,” he said.