Wild rain is set to lash Australia’s east coast with flood warnings have been issued for New South Wales and Queensland.

Australia’s east coast has woken up to its heaviest drenching in years as a major weather system causes flash flooding and strong winds. Roads are congested and train lines have closed.

A low pressure trough is dumping rain on a huge swath of the country with Byron Bay seeing its biggest downfall for almost half a century.

And there is to be absolutely no let up with an urgent weather warning now in place for an huge 1000km stretch of the coast from Sydney to Brisbane.

Sydney has had its wettest period since March last year with 70mm falling on the CBD overnight. More rain has fallen in six hours than has fallen in the last three months combined. The Harbour City could squelch its way through its wettest 24 hours stretch for years today.

A 2000km stretch of heavy rain caused flooding across Brisbane and southeast Queensland on Thursday with the weather system forecast to spread its way right along the east coast and hang around for days.

If the Bureau of Meteorology’s upper rain forecast is correct, Sydney could see just shy of 400mm of rain over the next week, which is more than three months’ worth of rainfall.

Flood warnings have again been issued for New South Wales and Queensland, with experts fearing an incredible 500mm of rain could be dumped on some areas over eight straight days.

By early Friday morning, Cape Byron – the easternmost point of mainland Australia – had received 272mm of rain in 24 hours – a feat not seen for 46 years.

Parts of Queensland are forecast to receive 500mm of rain after totals of almost 350mm in less than 24 hours.

The Wide Bay region has been hardest hit, with Mount Elliott recording 342mm between 6pm Tuesday and 1am Thursday.

Meanwhile, the massive wet front is dumping rain on parts of drought-ravaged NSW with authorities concerned heavier downpours in the north of the state could lead to flash flooding.

Collarenebri in NSW’s northwest recorded 45 millimetres in 24 hours.

Sky News Weather Chief Meteorologist Tom Saunders said the “heaviest rain in years” is starting to fall across many parts of the NSW coast this morning after lashing southeast Queensland over the past 48 hours.

“This major weather event will continue into the weekend,” he said. “Moisture from this system has been spreading south over the last 24 hours, even reaching the Victorian border.”

Queensland was the first to cop a hammering on Wednesday night. Tin Can Bay, in the Gympie Region for example, has already had 300mm of rain.

He said the rain is being caused by a very humid north-easterly air stream that’s “pumping” moisture to inland areas and even providing some “major drought relief” from some stricken towns.

Until Saturday, the north coast of NSW will be hit with possible flash and river flooding with up to 500mm tipped to hit.

The system is then forecast to veer south and spread over the length of the NSW coast.

Mr Saunders said it should be the wettest week for Sydney since March last year.

The downpour could also mark the heaviest February 24-hour rainfall in Sydney since 2002 – when 130mm of rain was recorded on February 5.

“There’s going to be a huge amount of rain,” he said. “It’s enough to extinguish some of the larger bushfires but not hard enough to fill up the dams, considering how dry the catchment has been.”

As of 11pm last night, there were still 42 fires burning across NSW. The RFS said they were “over the moon” to see rain arrive.

Today we were over the moon to see rain arrive across many parts of New South Wales, with decent fall in the State's north.



There are still 42 fires burning and 17 are yet to be contained. 1200 firefighters will continue working on these firegrounds tonight.#NSWRFS #NSWFires pic.twitter.com/xxNDkj97vV — NSW RFS (@NSWRFS) February 6, 2020

In Queensland, the wet weather will persist for the next eight days, with the southeast being the worst hit.

Many areas, particularly the coast, will see well over 100mm of rain over the next seven days.

Forecasters expect over 150mm of rain to fall on the Sunshine Coast alone, and on the Gold Coast and in Brisbane.

Meanwhile in WA, a severe heatwave being caused by a north-easterly air stream is taking temperatures higher than 40C in the state’s inland regions.

However, a cooler change from the west is pushing onto the coast, expected to drop temperatures today, when a tropical low should become a cyclone off the state’s north coast.

Mr Saunders said there’s a “fair amount of uncertainty” regarding the future track of the weather system, but it looked like the most likely scenario is that the cyclone would head toward the northwest coast over the weekend.

Back in NSW, Bureau of Meteorology have warned that flash flooding is possible when there is rapid rainfall, and residents in areas subject to flooding should keep up with the forecast.

“Heavy rain resulting in flash flooding along the coast is a real possibility,” NSW SES deputy commissioner Daniel Austin said, urging residents to prepare for the upcoming wet weather.

“Our focus will be the Northern Rivers and Mid North Coast areas, as well as further south later in the week as the weather tracks towards the Sydney Metropolitan area and the south coast,” Mr Austin said.

“Across those areas we are preparing for the possibility of flooding if rainfall levels are significant, in which case homes and businesses may be impacted. Preparing now for a flood can save lives and minimise the damage to property and possessions.”

Severe Weather Update: heavy rainfall and potential flooding for NSW & QLD.



Video is current at 11 am AEDT 5 February 2020.



For the latest weather and warnings, information visit https://t.co/ZwwnxWJFoM and follow advice from emergency services. pic.twitter.com/uBjtCUaEut — Bureau of Meteorology, Australia (@BOM_au) February 5, 2020

Here’s a look at the forecasts in the nation’s capitals.

Sydney will see a minimum of 10mm forecast to fall each day, and temperatures not expected to exceed 27C. The heaviest falls are expected on Sunday, with up to 60mm anticipated and the chance of thunderstorms.

Melbourne is in for a mostly sunny weekend, with the mercury getting as high as 30C on Saturday. The likelihood of receiving some rainfall will increase from Friday, with possible showers and thunderstorms forecast from the weekend into early next week.

Brisbane has a wet seven days ahead, with showers forecast every day and up to 70mm expected to fall in the city on Thursday.

Further south, Hobart isn’t likely to benefit from any wet weather until Saturday, with possible showers forecast into the weekend.

After horror fire and extreme heat conditions last week, Canberra will get some relief over the weekend, with showers forecast from Friday onward.

While Adelaide won’t see any wet weather in the coming days, showers and thunderstorms in Darwin will continue into next week.

With Natalie Brown, Frank Chung and Benedict Brook