'Life-threatening' flood warning as rain soaks country

Multiple flood warnings have been issued across NSW, the Northern Territory's northwest, Victoria and southern Queensland.

Sydney's outer west was part of a severe thunderstorm alert issued on Wednesday afternoon covering a swathe of northern and central NSW, including Katoomba, Orange and Dubbo.

Eyes were also on towns in and west of the Australian Alpine region, where storms and heavy rain were possible but intense deluges no longer likely.

Six-hourly rain totals of 50-80mm were likely, with motorists between Melbourne and Sydney possibly affected.

"The main risk associated with this storm is localised heavy rainfall leading to flash flooding and damaging winds," the State Emergency Service said.

Flooding has eased elsewhere in NSW including for 500 residents of Darkwood, near Coffs Harbour, cut off by a swollen Bellinger River until about midday on Wednesday.

Some rural properties on the Orana River, near Grafton, remain isolated but that river is also receding.

Further north, a severe weather warning was issued on Wednesday morning for Daly, Tiwi, Arnhem, Gregory and parts of Carpentaria, Barkly and Tanami districts.

Locations possibly affected included Darwin, Katherine, Nhulunbuy, Palmerston, Jabiru, Maningrida, Wadeye, Wurrumiyanga and Nauiyu.

In Western Australia, warnings have been issued for severe thunderstorms in the Kimberley region while 22,000 people in the Perth Hils and Wheatbelt remain without power after storms tore down hundreds of poles and wires on Tuesday.

"The damage area is massive, with seven transmission lines out of service," Western Power acting chief executive Jacqui Hall said.

"All available crews, including regional, have been deployed and we have called contractors in and mobilised helicopter patrols. All planned works have been cancelled where not critical."

Authorities are also warning of two tropical cyclones potentially developing in the coming days.

Anggrek is expected to become a category 2 system on Wednesday after forming in the Indian Ocean, about 4000km off Western Australia and is set to enter Australian waters this week.

"It is highly unlikely to have any impact on mainland Australia but gale force winds could be felt in the Cocos Islands," the bureau said.

A tropical low off Cairns is also set to strengthen into a cyclone by Sunday.

While expected to remain offshore this week, the system is a chance of tracking back toward Queensland's far north next week.

The region is still recovering from record flooding caused by Cyclone Jasper, with rain hampering progress.

Australian Associated Press