The NSW State Emergency Service (SES) says heavy to intense rain is still expected across large parts of the northern rivers region that may lead to life-threatening flash flooding.
More than 270 millimetres of rain fell overnight in parts of the northern rivers region.
The Bureau of Meteorology predicted further six-hourly rainfall totals between 70mm and 100mm, particularly in eastern parts of the forecast district.
Meteorologist Olenka Duma said there could be as much as 160mm over six hours in some areas.
Janet Petit from the SES Northern Zone said the rainfall, particularly isolated heavier falls, could lead to flash flooding.
"It will be widespread rainfall but those heavier falls are what we're concerned about, which will cause the life-threatening flash-flooding situations," she said.
"So it is important that people prepare their homes, stay off the roads over the weekend and keep your kids inside. It really isn't worth being out and about in these conditions."
The SES has responded to 135 jobs, including 10 flood rescues, since Wednesday.
Among them was a 61-year-old woman plucked from the roof of her car after she drove into floodwaters on Wyrallah Road near Lismore this morning.
"Some people have ... come around corners too quickly and have accidentally just driven in [to floodwaters]," said Ms Petit.
"While some people have actually taken the risk and driven through flooded causeways or flooded roads.
"I think we're going to see a few over the next few days, so just take care on our roads and slow down."
Flood alerts for local rivers
The BOM has issued a severe weather warning for heavy rainfall for the northern rivers forecast district, as well as parts of the mid north coast and northern Tablelands.
A moderate flood warning is in place for the Orara River and a minor to moderate flood warning is in place for the Tweed River.
Meanwhile, minor flood warnings remain in place for the Richmond, Wilsons and Brunswick rivers and Marshalls Creek.
There is a flood watch on the Clarence River.
Ms Petit urged anyone who needed help to call.
"Some units have them already packed and ready to go and if units are busy, they may say for you to come in and get them."
Ms Duma said these conditions were expected to remain in place across Friday and would start to ease over the weekend.
