Rain, wind and cooler conditions will continue to hit the NSW east coast this week, heightening the risk of flash flooding and hazardous surf conditions.
"A trough that has brought rain and showers since Friday ... will continue until at least next weekend," the Bureau of Meteorology said.
The NSW SES received almost 200 calls for help in the past 24 hours and three millimetres of rain had already hit Sydney on Monday morning.
The bad conditions will continue to buffet the coast with gusts of up to 70 to 80 km/h likely.
Temperatures have dropped to around 15 degrees, down about eight degrees for this time of year, due to a cold front which saw almost 10 centimetres of snowfall in the alps.
"We do have some hazardous conditions at the moment for the beaches with the strong southeasterly winds whipping up a bigger southeasterly swell up to around four, potentially five metres," BOM spokeswoman Rebecca Kamitakahara told ABC radio.
"The good news is later in the week we will start to see a little more sunshine ... with those temperatures coming back up to what we'd normally expect at this time of year."
But the rain has brought relief for farmers across the western ranges and areas west and southwest and parts of the central west.
"They're not seeing as quite as high rainfall totals as what we're getting on the coast but they are still seeing some more steady, persistent rain on top of what they saw on the weekend." Ms Kamitakahara said.
The rain overnight resulted in the closure of several roads in Sydney's north, with Wakehurst Parkway shut in both directions from Oxford Falls to North Narrabeen, due to flooding.
Galston Road is closed in both directions after a rockfall west of a bridge and drivers are being told to divert.
A severe thunderstorm and heavy rain warning that could lead to flash flooding, damaging winds and large hailstones has been issued for Lismore, Grafton, Casino and Yamba on the state's north coast.
Gale warnings have been issued for the Hunter coast, Sydney coast and Illawarra coast alongside strong wind warnings for Sydney waters, the Macquarie coast, Batemans coast and Eden coast.
A damaging winds warning has been issued for parts of the southern tablelands, south west slopes, Snowy Mountains and Canberra.
Surf and swell conditions will be hazardous for rock fishing, boating, and swimming with NSW Police warning people to stay out of the water and avoid walking near surf-exposed areas.
Australian Associated Press