Residents on parts of Sydney's northern beaches were told to leave their homes after rapidly rising floodwaters impacted several properties.
The evacuation orders forced locals and holiday makers near Narrabeen Lagoon to head to higher ground on Saturday night, although warnings were downgraded on Sunday morning.
Widespread, heavy rainfall led to parts of the city's northern beaches and the Central Coast receiving up to 200 millimetres of rain in the 24 hours to 9am on Sunday.
Floodwaters at Narrabeen are expected to take several days to recede.
The NSW State Emergency Service made 25 rescues of people trapped in floodwaters across the state, many in Sydney, as cars became submerged on inundated roadways.
At Great Mackerel Beach, an isolated outpost on the northern beaches that is accessible only by boat, a landslide damaged numerous homes and at least one person was injured.
Other regions such as Goulburn, in the NSW Southern Tablelands, were smashed with hailstorms.
The storm system claimed the life of a woman on Saturday after a tree branch fell on her car on Macquarie Pass, southwest of Wollongong.
At least 1000 SES volunteers were on the ground on Sunday responding to weekend call-outs, with the busiest units in the south coast, Illawarra, Sydney and Hunter regions.
NSW SES spokeswoman Emily Barton told AAP rain had been experienced "far and wide" across the state.
As of 10am on Sunday, she said crews had responded to over 2100 incidents, mostly in Sydney and the surrounding area.
"We've got about 1000 SES volunteers that have been active during this operational response, and they remain ready to respond to any further calls for assistance," Ms Barton said.
"We've got high-clearance vehicles and flood rescue teams that are on standby, particularly through metropolitan Sydney and the Central Coast regions, where we're expecting to see the rainfall continue today.
"But storms are possible anywhere north of Wollongong and thunderstorms could bring those isolated, intense rainfalls that we saw late last night in the northern beaches and the Central Coast."
Ms Barton said clean-up efforts would continue over the next 24 to 48 hours, with further severe thunderstorms forecast for later in the week.
Warnings remain in place for hazardous surf on the east coast at beaches stretching from Newcastle to Batemans Bay, as well as the Eden coast.
Senior meteorologist Dean Narramore said the coastal trough that caused the storms stalled over the Central Coast, leading to repeated downfalls.
"That's why we just had storm after storm going over the same area, dropping 30 to 50mm each time," he said.
"After four or five of those, some places racked up to 200mm which has led to quite a bit of flooding."
Rain was expected to continue early on Sunday afternoon with thunderstorm warnings in place around Sydney and Newcastle, but conditions would start to ease late in the afternoon.
Queensland also experienced significant rainfall in two parts of the state, with Port Douglas receiving 109mm and more than 60mm dumped across the southeast.Â
Further thunderstorms are expected on Sunday, while more than 2000 properties remain without power in the Lockyer Valley.
30°C