Emergency responders in NSW are preparing for more flood rescues as severe weather brings renewed dangers across much of Australia – with up to a month’s rain to fall by Thursday.

Severe weather warnings for heavy rain were current for NSW, parts of Victoria and southern Queensland on Tuesday afternoon, bringing renewed flood threats to all three states.

The Bureau of Meteorology warned that forecast rain was likely to lead to rises on many already flooded rivers in NSW, Victoria, and southern Queensland, with widespread moderate to major flooding likely across inland NSW.

“We’re looking at around a month or more worth of rain, particularly across inland areas in NSW,” the BOM’s Gabrielle Woodhouse said on Tuesday.

Two significant weather systems will bring thunderstorms and high rainfall totals of up to 50 to 80 millimetres across NSW in coming days.

“We’ll start to see more of a flash flood risk as well as riverine flood risk,” Ms Woodhouse said.

“There is a lot of rain and … it’s falling on very very wet catchments.”

Forecaster Weatherzone warned of widespread falls of 20-40 millimetres across the Northern Territory, western Queensland, NSW, northern Victoria and South Australia on Tuesday and Wednesday – with some areas getting as much as 80 millimetres.

“Some of the heaviest falls are expected over the Murray-Darling Basin, where most rivers are already at the moderate flood level, with some areas experiencing major flooding,” it said on Tuesday.

“After a brief reprieve, a cold front will clip south-western Western Australia from Wednesday. This front will link up with more moisture from the north over SA on Thursday and continue to build into the weekend as it crosses eastern Australia.

“Flooding rains once again look to fall over Friday, Saturday and Sunday over much of NSW, Victoria and into northern Tasmania. Widespread falls of 30-60 millimetres are expected, though some locations could see more than 80 millimetres. Severe storms and gusty winds will follow the heaviest rain.”

Rain and thunderstorms hit inland NSW earlier on Tuesday, with a severe weather warning for heavy falls and a risk of flash-flooding covering much of the state’s west, from Nyngan in the central north, to Deniliquin near the Victorian border, through to Broken Hill in the central west.

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There were also widespread storms across South Australia, where the SES said it was “responding to a large number of jobs as a weather front moves southwards”.

“Strong, gusty winds resulted have resulted in a number of trees down in the northern, eastern and southern suburbs [of Adelaide],” it tweeted.

“Crews may be delayed in responding to your call, please be patient.”

On Monday, the SA SES began handing out sandbags in some parts of the state, ahead of forecast heavy rain.

The weather system was expected to shift on Tuesday afternoon bringing widespread, heavy falls east on Wednesday before weakening on Thursday as it moved south.

On Wednesday, western and south-west Queensland, western and central NSW and northern and north-eastern Victoria can all expect downpours. Moderate falls are also possible along the NSW south coast.

A second system will bring more rain on Friday, with a widespread deluge forecast for NSW’s western slopes and ranges, continuing to the coast on the weekend.

The drenching will not be as severe on the NSW north coast. But more severe rainfall could develop, along with high winds and heavy waves, as the low-pressure system develops towards the weekend.

The SES was concentrating on key communities as it expected to cop flooding in western and central NSW towns, including Gunnedah, Wee Waa and Warren this week.

Nyngan, about an hour from Warren, was also being monitored closely, SES Commissioner Carlene York said.

Major rivers of concern include the Namoi, the Darling, Culgoa, Bogan and Barwon rivers. The SES has urged anyone travelling in those areas to be prepared.

A stranded driver was rescued by SES volunteers on Monday after trying to drive across a flooded roadway, Ms York said.

As the NSW school holidays came to an end this weekend, she urged people to drive with care, and not to drive across flooded roadways.

-with AAP