Several people have been rescued from floodwaters as heavy rains lash parts of the NSW coast.
Four vehicles were pulled from floodwaters in the Hunter Region on Wednesday, the State Emergency Service says.
The SES responded to almost 400 emergency calls throughout the day as more than 100 millimetres of rain fell overnight across the Hunter and Mid North Coast.
A severe weather warning remains in place for those regions and the Northern Tablelands.
Both the Williams and Paterson rivers are expected to swell under heavy rain as the coastal trough brings widespread rainfall for the next two days.
Residents of Dungog, where three people died in the 2015 floods, have been issued with warnings, an SES spokesman told AAP.
The small town is a "magnet" for this type of weather, bureau meteorologist Ashleigh Lange said.
Low-lying bridges and roads are expected to be submerged but no properties in the town are expected to be affected.
Farmers in the Hunter have been advised to move cattle to higher pastures with some farms tipped to be isolated from flooding.
The heavy rain is forecast to move north as far as Coffs Harbour before easing on Friday, according to the BOM.
Flash flooding is possible while gusty winds are also likely to create hazardous surf conditions.
Wet and windy weather is expected from Coffs Harbour to Wollongong on Wednesday and Thursday.
Offshore strong winds are also expected to create hazardous surf conditions for the Hunter and Sydney coasts.
"We do expect that many places will get their normal monthly rainfall for March in just a couple of days," bureau meteorologist Adam Morgan told AAP.
People are being urged to avoid non-essential travel once the severe weather starts, and to bring pets indoors and cars under cover.
Those driving are encouraged to slow down, take extra care and avoid driving in floodwaters.
