With more heavy rainfall on the way, the SES is urging NSW residents not to drive, ride or walk in floodwaters after they were forced to rescue almost 60 people and pets over the past 24 hours.
By Friday afternoon, the SES had responded to about 800 calls for assistance as a low pressure system wreaked havoc along the coast, with more than 450 of those callouts in the Illawarra and Shoalhaven region.
SES spokesman Brent Hunter says most of the 59 rescues involved people who were driving through floodwaters, something the SES doesn't condone.
"It's probably the most dangerous thing you can do during these sort of events," Mr Hunter said.
In the Illawarra region on Friday morning, the body of 11-year-old Ryan Teasdale was found in a creek bed at the end of a stormwater drain.
He had been sucked into the drain while playing at a Unanderra park more than 18 hours earlier.
Superintendent Zoran Dzevlan said heavy rainfall and subsequent torrents of water rushing through the drains overnight were factors in the boy's death.
Heavy rain is expected to continue on Saturday with the Bureau of Meteorology forecasting more than 100 millimetres over the next 24 hours on the mid north coast, parts of the Hunter and Northern Tablelands.
Towns potentially affected include Coffs Harbour, Port Macquarie, Taree, Newcastle, Satwell and Dorrigo, the BOM said in a severe weather warning issued at 4.30pm.
In Sydney, officials are confident Saturday's Golden Slipper meeting will go ahead at Rosehill despite the forecast for more rain.
The Australian Turf Club's general manager of tracks, Lindsay Murphy, said the western Sydney track could cope with more rain before Saturday.
"It hasn't been a bad day - we've had a lot of wind and not much rain," Ms Murphy said.
"The meeting will definitely go ahead as planned unless we get more rain on the day but hopefully it is coastal."