Sydney, Melbourne, Brisbane weather: Severe rain warning issued 

Aussies are being warned to brace for a wet week as an unfolding weather system brings severe storms, heavy rainfall and potential flash flooding.  

The unseasonal rain event, which affected western and central Australia earlier this week, is expected to move towards southeastern Australia starting Wednesday.

Bureau of Meteorologist Johnathan How explained a cold front approaching Victoria and Tasmania would link up with tropical moisture bringing extensive rain to the countrys southeast. 

Thursday looks to be the wettest day of the outlook, particularly across eastern parts of NSW, Mr How said. 

Moderate to heavy rainfall is expected across a large part of the state, extending from the Illawarra region up through Greater Sydney and the Greater Hunter areas, with up to 40mm of rain forecast for Sydney.

Canberra is also expected to see its wettest day on Thursday, with up to 25mm of rain, while Brisbanes heaviest rain is forecast for Friday, with up to 20mm. 

On Friday, the rain will then shift to northeast NSW and eastern Queensland, with modelling indicating a low-pressure system could boost totals anywhere between 100 to 200mm. 

Australias south eastern coast is set for a soaking as two weather systems bring heavy rain and gusty winds 

At this stage, there is enough model consensus to suggest that the heaviest rain, strongest winds and largest waves will probably occur along the mid north coast and possibly in parts of the Hunter or Northern Rivers districts, explained Weatherzone Meteorologist Ben Domensino

While there is noticeable disagreement in the location of the heaviest rain, models are predicting localised rainfall totals of more than 20 mm from this system. 

This would be enough rain to cause flash flooding.

Dramatic temperature fluctuations can also be expected this week as the mercury swings from spring heat to wintry weather due to the cold front sweeping north.

Perth will see a maximum temperature of 30C on Thursday before dropping by more than 10C to a cool 19C on Friday. 

Melbourne and Canberra reached 25C on Tuesday - the warmest day since Autumn -before dropping on Wednesday to 15C and 20C, respectively.

Sydney is forecast to reach 31C on Wednesday, which is 11C above the months average, before plummeting to a cool 18C on Thursday. 

Wednesdays burst of spring heat, coupled with gusty winds, has elevated the fire danger for parts of NSW including the Great Sydney, Illawarra and Shoalhaven region.  

 Bureau of Meteorologist Johnathan How explained a cold front approaching Victoria and Tasmania would link up with a tropical moisture bringing extensive rain to the countys south east from Wednesday

Thursdays is expected to bring the heaviest rainfall to Sydney, with up to 40mm of rain

Sydney

Wednesday: Partly cloudy. Medium chance of showers. The chance of a thunderstorm. Winds up to 30km/h. Max 30C. 

Thursday: Rain. Windy. Up to 40mm of rainfall. Winds up to 40km/h. Large and powerful surf conditions in the evening are expected. Min 13C Max 18C.

Friday: Rain. Up to 25mm of rainfall. Winds up to 30km/h. Min 13C Max 19C. 

Melbourne 

Wednesday: Rain. Up to 15mm of rainfall. Winds up to 25km/h. Max 15C.

Thursday: Cloudy. Slight chance of a morning shower. Winds up to 35km/h. Min 9C Max 14C. 

Friday: Sunny. Patches of morning frost. Light winds. Min 6C Max 17C.

The near nationwide soaking is due to a spring north-west cloudband which brought rain to the northern parts of Western Australia and central Australia before moving east 

Brisbane 

Wednesday: Mostly sunny. The chance of smoke haze inland. Winds up to 25km/h. Max 27C. 

Thursday: Partly cloudy. Medium chance of showers in the evening. Winds up to 25km/h. Min 16C Max 29C. 

Friday: Rain. Up to 20mm of rainfall. Winds up to 20km/h. Min 17C Max 22C.

Canberra 

Wednesday: Rain. Up to 15mm of rainfall. Winds up to 30km/h. Max 20C. 

Thursday: Rain. Up to 25mm of rainfall. Winds up to 25km/h. Min 3C Max 12C. 

Friday: Partly cloudy. Slight chance of a shower. Winds up to 30km/h. Min 2C Max 15C.

Hobart 

Wednesday: Partly cloudy. Medium chance of showers, most likely in the evening with possible small hail. Winds up to 30km/h. Max 14C.

Thursday: Cloudy. Slight chance of a shower. Possible small hail in the morning. Winds up to 30km/h. Min 4C Max 13C. 

Friday: Partly cloudy. Winds up to 20km/h. Min 4C Max 17C. 

Dramatic temperature fluctuations can also be expected this week as the mercury swings from spring heat to wintry weather due to the cold front sweeping north

Perth 

Wednesday: Sunny. Winds up to 30km/h. Max 24C. 

Thursday: Sunny. Slight chance of a shower. The chance of a thunderstorm in the afternoon and evening. Winds up to 40km/h. Min 15C Max 30C. 

Friday: Showers. Up to 15mm of rainfall. Winds up to 35km/h. Min 13C Max 19C.

Adelaide 

Wednesday: Cloudy. Medium chance of showers. Winds up to 35km/h. Max 18C. 

Thursday: Sunny. Slight chance of a shower in the early morning. Winds up to 30km/h. Min 7C Max 18C. 

Friday: Sunny. Winds up to 20km/h. Max 21C.

Darwin

Wednesday: Mostly sunny. Winds up to 20km/h. Max 34C. 

Thursday: Partly cloudy. Medium chance of showers. The chance of a thunderstorm inland. Winds up to 20km/h. Min 25C Max 33C. 

Friday: Partly cloudy. Medium chance of showers. The chance of a thunderstorm. Winds up to 20km/h. Min 25C Max 33C.