Western Sydney could be in for minor flooding after Warragamba Dam spilled over following a weekend of heavy rain.


A State Emergency Service (SES) spokeswoman says the spillover occurred about 3.30am (AEDT) and could cause flooding in local areas.


"Penrith could be affected and the Richmond areas today on the Hawkesbury Nepean River," she said.


Minor flooding could disrupt local ferry services and close low roads and bridges.


Warragamba Dam serves as Sydney's main water reservoir and does not serve a dual role as a flood mitigation dam as is the case for Brisbane's Wivenhoe Dam. Queensland authorities yesterday began releasing more water from Wivenhoe as the region braces for heavy rains over the next few days.


As swollen creeks and rivers start to recede across NSW, the SES says 26,000 people remain stranded by floodwaters in the north but the focus now is shifting to recovery and resupply.


Crews from the SES, NSW Rural Fire Service and Fire and Rescue NSW are concentrating on the Sydney suburbs of Malabar and Narellan, and Kiama on the south coast, which were worst-affected by storm damage over the weekend.


In Kiama, three houses were destroyed and seven others badly damaged, while St Andrew's Primary school at Malabar will be closed on Monday for safety checks.


Meanwhile Ausgrid crews are working to restore power to about 500 homes and businesses on the Central Coast, about 100 in Sydney and more than 500 around Kiama and Bowral.


At its peak over the weekend, more than 6000 homes and businesses on the Central Coast were without power as trees and debris hit powerlines.


AAP