Sydney has received its heaviest two-day rainfall in 19 months and can expect showers to continue throughout Wednesday morning.

NSW emergency services have received almost 600 calls for help in the past 24 hours as the wild weather lashes Sydney and other parts of the state.

The NSW State Emergency Service said it had fielded about 590 calls over the past day, mostly from residents in Sydney's north, which has endured heavy rain since Tuesday.

SES spokesman Phil Campbell said the SES had received reports of flash flooding and leaking roofs in the area, but not any relating to significant property damage.

"We've been quite lucky, there's not been much wind with this weather system," Mr Campbell told AAP.

The CBD has recorded 59 millimetres of rain since 9am on Tuesday, and 92 millimetres since the morning of Australia Day.

The last time rainfall was as heavy  over two days was in June 2013, while a similar downpour occurred in January that year.

Sydney's north shore and northern beaches have received the heaviest falls in the past 24 hours.

Chatswood recorded 83 millimetres, while Frenchs Forest (82mm), Hornsby (79mm) and Terrey Hills (78mm) also received a drenching.

Weatherzone: Sydney radar

These areas all recorded more than 100 millimetres in the past two days, the heaviest falls being at Castle Cove, which recorded 144 millimetres.

Senior meteorologist at Weatherzone Anthony Duke said the heavy rainfall was not "completely unheard of" but warned motorists and people dropping children off at school to expect delays.

"It will be a similar commute to yesterday," Mr Duke said.

"We've got quite a few schools back now and, with the amount of rainfall on the roads, there's going to be a lot of spray about.

"Today we should see the showers becoming more isolated and looking like we could see the last of the showers through the afternoon."

An odd shower is expected to redevelop overnight, but Sydneysiders can expect drier weather leading into the weekend. In the north-west of the state, some towns are expected to receive 20 to 50 millimetres.

A top of 23 degrees is forecast for Sydney on Wednesday and temperatures will remain steady throughout the week.

"We're probably going to get a few [showers] most days but the trend is also warming, so by the time we get to Saturday we are looking at the high 20s, possibly the low 30s for the western suburbs," Mr Duke said.

- with AAP

Weatherzone is owned by Fairfax Media, publisher of this website.