Multiple states warned of severe thunderstorms, heavy rain, as weather system moves north

Residents have been warned to prepare for thunderstorms and heavy rain forecast to hit NSW earlier than previously expected.

A low-pressure system causing widespread rain across South Australia was moving north into NSW and parts of Queensland today.

The Bureau of Meteorology issued a severe thunderstorm warning for NSW this afternoon, following earlier reports the storms wouldn't hit the state until tomorrow.

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Between 50 and 100 millimetres of rain, dangerous thunderstorms and damaging winds are expected.

The Central West Slopes and Plains, Riverina and Upper Western districts, Southern Tablelands, parts of the Snowy Mountains, Australian Capital Territory, South Coast and South West Slopes districts have been warned to expect heavy rainfall and potential flash flooding.

The State Emergency Service issued additional flood warnings and warned residents in the affected areas to buckle down for storms expected to last until tomorrow.

"The most important thing the community can do is to avoid travelling through flood waters," NSW SES senior manager for state operations Chief Superintendent Dallas Burnes said.

"You don't know what debris or damage to the road could be below the surface.

"The best rescue we do is the one we don't have to do because the community is making sensible decisions."

Minor flooding is possible in the following areas:

• Illawarra Coast, St Georges Basin, Clyde River, Moruya and Deua Rivers, Tuross River, Peel River, Namoi River, Castlereagh River, Macquarie River to Bathurst, Orange, Molong and Bell River
• Turon and Macquarie Rivers to Burrendong Dam, Macquarie River down steam of Burrendong Dam, Bogan River, Tumut River, Upper Murrumbidgee River to Burrinjuck Dam and Cooma Creek
• Murrumbidgee River to Wagga Wagga, Mirrool Creek, Queanbeyan and Molonglo Rivers, Snowy River, Upper Murray and Mitta Mitta Rivers

Moderate flooding is expected for the Bega River.

"We're expecting sustained rainfall across large parts of the state, and we are concerned about the potential of riverine and flash flooding," Burnes said.

"We've prepositioned assets to the areas we are most concerned about, and we've reached out to our interagency partners to prepare their teams should they need to stand up and assist us in our response."

South Australia

South Australia was first in the firing line from the wild weather, with Adelaide receiving a months' worth of rain in six hours.

More than 35 millimetres of rain fell yesterday, causing flash flooding and the wettest November day in 59 years.

The Bureau of Meteorology issued a severe thunderstorm warning for metropolitan Adelaide and surrounding areas earlier this morning, as thousands of homes and businesses remain without power.

Planes were grounded at Adelaide airport causing delays, roads disappeared under water and parked cars were flooded in.

Entire suburbs were drenched, with some backyards engulfed by water.

"It was like a tidal wave, coming down here, it was just cascading through here," one Wayville local said.

The deluge was a result of two weather systems that collided from north and south to create the perfect storm, and more than 250 calls were made to South Australia's SES.

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Victoria can also expect strong gusts at Port Phillip, Gippsland Lakes, West Coast, Central Coast, Central Gippsland Coast and East Gippsland Coast.

In Queensland, there is a major flood warning for Moonie River and a moderate warning for Wallam Creek in south-west Queensland.

November has brought widespread rain and thunderstorms over part of every state and territory in Australia.

Some parts of Queensland, NSW, the Northern Territory, South Australia and Western Australia have already collected more than three times their average November rainfall.

- With Weatherzone