Trains are delayed across Sydney and emergency calls are spiralling as two major storm systems dump torrential rain on NSW – with falls expected to get heavier from Friday afternoon.

Damaged equipment at Redfern station in inner-Sydney on Friday was blamed for widespread rail delays, while dozens of flights in and out of the city’s international airport were cancelled, and schools were closed across the state.

The Bureau of Meteorology said conditions were expected to worsen as the day wore on and the trough deepened – Sydney may get a month’s rainfall in just 24 hours. Immediate concern is focused on greater western and southern Sydney, the Blue Mountains and the Illawarra.

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

“We have had a lot of rain today, but our fear is for a bigger amount of rain this evening, where we think we’ll see the [Hawkesbury] river rise,” Hawkesbury City mayor Sarah McMahon told the ABC.

“We’ve very concerned for business owners who operate on the flood plain, our farmers and, of course, residents who have low-lying homes.

“There’s a lot of businesses and homes in the eye of the flood. It does depend on the flood level as to how many may be inundated. So, we are bracing for whatever may come over the next few days.”

There were minor to major flood warnings for the Hawkesbury and Nepean rivers on Friday, with moderate to major flooding likely along the Colo River.

For the Hawkesbury, the situation is complicated by the Warragamba Dam, Sydney’s main reservoir. The dam, on the city’s south-western fringe, was 96.3 per cent full on Friday morning and is likely to spill by Monday.

Water NSW chief executive Andrew George said 90 millimetres of rain would fill the dam.

“We’re expecting 100 millimetres to 150 millimetres,” he said.

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

Elsewhere on Friday, power was cut to a major city-centre court complex after the rain affected local electricity infrastructure.

Transport for NSW advised people to delay non-essential travel on the roads and recommended boaters remained ashore as the dangerous storm system travelled along Australia’s eastern seaboard.

The NSW SES has advised residents to stay indoors.

Across the northern border, there are also also warnings for parts of south-west Queensland with river levels expected to rise above a moderate level at Charleville later on Friday because of multiple days of heavy rainfall.

Floodwaters are not expected to exceed levee levels at their peak, leaving the town protected from inundation.

There is a severe weather warning along the NSW coast 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 as far south as Wollongong and west as Griffith and Cobar. Wind gusts could reach up to 90km/h south of Sydney on Friday night.

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

There had been 90 millimetres of rain at Taree, on the mid-north coast, since 9am on Friday, while further north at Port Macquarie nearly 84 millimetres had fallen.

At Lismore, in the northern rivers region, a man taking his chances with flooded roads on the way to visit his wife in hospital ended up stuck with water up to the roof of his four-wheel drive. The river had risen quickly overnight, according to retired lawyer Keith Graham, who swam out to save the man.

“I have no idea what he was thinking,” Graham said.

It was one of several car rescues in recent days and followed the death on Wednesday night of 71-year-old grandfather Peter Wells, who appeared to have driven into a swollen creek in Logan, south-west of Brisbane.

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

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 night, the SES warned.

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

The SES had responded to 823 incidents by Friday afternoon, including seven flood rescues.

“With the intense rainfall and also the very strong winds that are predicted … we will expect trees to be uprooted and we’ll have structural damage to buildings,” SES deputy commissioner Deborah Platz said.

-with AAP