Trains are facing delays due to damaged equipment at Redfern station in inner-Sydney, while dozens of flights in and out of the city’s international airport have been cancelled.

Power was also cut to a major city-centre court complex after the rain affected local electricity infrastructure.

Transport for NSW has advised people to delay any non-essential travel on the roads and recommends boaters remain ashore as the dangerous storm system travels along Australia’s eastern seaboard.

The NSW SES has advised residents to stay indoors.

A severe weather warning is in place along the NSW coast stretching from Morisset, south of Newcastle in the Hunter, down to Bega on the South Coast and extending west to the Central and Southern Tablelands past Oberon and Goulburn.

Severe thunderstorms are possible from the Queensland border south to Wollongong and west to Griffith and Cobar.

Wind gusts could reach up to 90km/h south of Sydney on Friday evening.

Minor to major flood warnings are in place on the Hawkesbury and Nepean Rivers with moderate to major flooding likely along the Colo River.

The NSW State Emergency Service has 45 warnings in place, including a watch and act for residents of Darkwood on the mid-north coast to prepare to be isolated by flooding.

Further south at Port Macquarie, more than 50mm of rain has fallen since 9am on Friday.

The rain is expected to shift further south, easing throughout Saturday before moving over the Tasman Sea, however flood dangers linger.

Warragamba Dam – which serves as Sydney’s main reservoir – is likely to spill on Monday, Water NSW chief executive Andrew George warned.

“We require about 90mm of rain to fill Warragamba Dam … we’re expecting 100mm to 150mm,” he said.

“The spill will occur likely when the rainfall event has moved on, so it is very important that the community remain vigilant.”

The dam, on the city’s south-western fringe, was 96.3 per cent full on Friday morning.

An inland low and coastal trough joining forces over NSW are driving the deluge.

“We’re expecting the interaction between these systems to really increase the rainfall over eastern NSW,” the Bureau of Meteorology’s Helen Reid said.

The ongoing intense downpours would drive “dangerous and life-threatening flash flooding” from Friday evening, the SES warned.

Residents of Sydney, Gosford, Wollongong, Nowra, Batemans Bay and Goulburn are urged to stay indoors during the dangerous weather.

In Sydney’s city centre, 111mm of rain fell in the 24 hours to 9am on Friday.

The SES responded to 552 incidents in the 24 hours to 5am on Friday, including seven flood rescues.

Premier Chris Minns advised residents to remain alert and up-to-date with warnings in their local areas.

“It is a volatile event and we need to make sure that we’ve got the latest information … but it does require everybody being alert, particularly in the next 24 to 48 hours,” he said.

The storm has already claimed a life in Queensland after a man was found dead by his ute near Logan, while a 30-minute downpour in northern NSW flooded enclosures at a wildlife sanctuary on Thursday.

“Due to the amount of water dumped into the park, we have relocated our animals and the hospital (has been) re-located to a higher position,” Byron Bay Wildlife Sanctuary said.

The sanctuary has since received more than $11,000 via an online fundraiser.