There is a growing flood threat across eastern Australia, while in Western Australia, heat wave conditions will impact on Perth. In the north of Western Australia, coastal communities will be on alert due to the potential for a tropical cyclone to form.

Widespread rainfall of 50-150mm has caused major flooding in parts of NSW and minor flooding in south-east Queensland.

Bellingen in NSW has had a bucket-full, with 167mm in the 24 hours to 9am today, while Upper Darkwood to the west gained 178mm, Weatherzone meteorologist Douglas Fenton said.

Dorrigo was inundated with as much as 100mm in just one hour and 209mm during the past 24 hours, their heaviest rain since May 2009, he said.

These very high rain totals have led to major flooding on the Bellinger River at Thora, with river levels continuing to rise this morning.

In Queensland, Bribie Island received some of the heaviest falls with a daily total of 130mm to 9am today. Hotham Creek to the north of Coomera was drenched with 125mm in the 24-hour period. The scattered persistent rain led to minor flooding on the Paynter River at Diddlibah, inland of Maroochydore.

Several severe weather alerts and storm warnings have been issued for NSW and Queensland due to flash flooding. The recent rainfall has saturated the land along the coast and nearby inland and so the bulk of the water has nowhere to go but along the surface.

The outlook is for the wet weather to continue for the eastern seaboard over the next several days, particularly along the coast and adjacent ranges.

The rain will be focused from the Queensland Capricornia district down to the NSW mid north coast. Rain totals from today to Friday are likely to range from 300-400mm in parts.

"South-east Queensland and north-east New South Wales are in for a prolonged deluge of rain, with the potential for widespread falls of over 200mm for areas between Bundaberg in Queensland and Port Macquarie in New South Wales by the end of the week," Alex Zadnik, senior meteorologist at Weatherzone, said.

"Some towns will see even higher rain totals in the 300-400mm range over the next six days, bringing a significant threat of both flash flooding and river flooding," Mr Zadnik said.

"We have a stationary high pressure system in place over the Tasman Sea, which is going to send a persistent flow of moisture-laden air into both Queensland and New South Wales.

"The entire lower portion of the atmosphere is going to become saturated during the first half of this week, setting the scene for torrential rainfall when a deepening low pressure trough forms along the eastern seaboard," he said.

Heat alert

For the west coast of Western Australia, weather conditions will be in stark contrast, with extended heat wave conditions.

Heat waves can have the greatest toll on human life of any weather phenomena, with the very young and elderly at greatest risk.

"Using the most widely accepted heat wave definition of at least five days in a row with maximum temperatures of five or more degrees above average, Perth is certainly going to qualify," Mr Zadnik said.

"Perth's average maximum temperature in January is 30.9 degrees and the forecast is for temperatures near 40 degrees between Tuesday and Sunday.

"If the temperature gets past 40 this week as expected, it will be the hottest weather so far this summer, with the previous highest being 39.9 degrees back in December," he said.

While Perth is sweltering through an extended run of heat, communities along the north-west coastline of Western Australia will be monitoring the formation of a tropical low over the Indian Ocean.

"A monsoonal low over the Indian Ocean is expected to intensify into a tropical cyclone by mid to late week (likely to be named Iggy), with the potential for a coastal impact towards the weekend.

"There is still uncertainty around the future movement and strength of this system, although the Pilbara coastline would be the area singled out for being most at risk," Mr Zadnik said.

Source: Stuff.co.nz

RIVERS BURST AND TOWNS FLOODED