UPDATE 3pm:
The State Emergency Service have responded to 298 calls for help across the state with the majority for damaged roofs and fallen trees.
Sydney is one of the worst areas affected with 171 calls.
Volunteers are preparing for a busy night with the worst of the wind and rain expected to develop overnight and into Tuesday.
Crews have responded to 13 jobs in the Sutherland Shire.
A fallen tree on lines near Wolli Creek has delayed trains on the Eastern Suburbs and Illawarra line. Services are running up to 10 minutes late. There are also delays on the Southern line after a tree came down at Corrimal.
Since 9am Cronulla has received 14 millimetres of rain while Sans Souci has received 16 millimetres.
UPDATE 10am:
If you think it was wet on the way into work this morning, it's likely you'll be in for a shock on the way home.
The Bureau of Meteorology has issued a severe weather warning for damaging winds along the coastal fringe for later in the day, with gusts expected to reach 100km/h in the metropolitan, Illawarra and Hunter forecast districts.
Sydney has recorded about 13mm in the CBD since midnight, and the bureau is predicting 20-50mm on Monday, with winds strengthening.
"This afternoon it'll peak, which won't be good for umbrellas or for traffic," Rob Sharpe, a meteorologist with Weatherzone said.
Sydney and much of the NSW coastline are in for a wet and windy couple of days as a big east coast low forms just offshore.
"We'll definitely see trees down with this system," Mr Sharpe said. "This is going to be our most significant east coast low since spring."
Wind gusts have already reached 100km/h at Wattamolla to Sydney's south, while Kurnell and Sydney Airport have both had winds of 65km/h.
Rainfall is likely to intensify as a cold air mass interacts with a coastal trough off the NSW coast, spawning the deep low.
Weather models disagree as to how far off the coast the low will develop and how fast it will move away, but rainfall totals should total about 100-300mm from Sydney to Foster over the next 48 hours, Mr Sharpe said.
The winds would pick up for the city on Monday afternoon, making for a tough commute home for workers, he said.
Rainfall totals are likely to be heavier north of Sydney on Tuesday, with the Newcastle area likely to be wettest, the bureau said:
Some western suburbs such as Penrith may see only a chilly top of 15 degrees on Monday although the wind chill will be less than on the coast.
The CBD should get a top of 18 degrees on Monday and Tuesday before conditions improve, with rainfall easing to showers and temperatures starting to pick up towards a maximum of 25 degrees on Friday.
The east coast low is probably going to move away fairly quickly late on Tuesday although one model has it lingering longer, extending the wet conditions for Sydney, Mr Sharpe said.
EARLIER STORY:
Damaging winds of up to 100km/h and dangerous surf conditions are expected in Sydney this afternoon, Monday, April 20.
The State Emergency Service reminds people to move cars under cover or away from trees, secure loose items and keep clear of fallen power lines.