Massive downpour to strike 80 per cent of Australia - here's when it will hit Sydney, Brisbane and Melbourne

Millions of Aussies are set to be lashed by wet weather as a rain band sweeps through the country's east.

Sky News Weather presenter Lucy Polkinghorne said 80 per cent of the country will likely be hit by wet conditions this week.

'This rainband will continue moving eastwards into the week, increasing cloud cover over the eastern half of the country by Tuesday then bringing much cooler and showery conditions,' Ms Polkinghorne said.

'In fact, 80 per cent of the country will likely see some wet weather from this event.'

Rain is forecast for Sydney from Wednesday and Thursday, with lighter falls expected on Friday, according to the Bureau of Meteorology.

A high of 30C is expected for the start of the rain event on Wednesday before temperatures drop to 18C and 19C at the end of the week.

Melbourne is bracing for rain on Tuesday until Thursday before it clears on Friday.

Adelaide residents can expect to cop rain on Tuesday and Wednesday, before the sun breaks through on Thursday and Friday.

Hobart can expect a possible shower on Wednesday and Thursday.

Meanwhile in Brisbane, rain is forecast for Thursday and Friday.

Tuesday: Mostly sunny. The chance of fog in the early morning, mainly in the west. Light winds becoming northeasterly 15 to 20 km/h in the early afternoon then becoming light in the evening. Min 14, Max 27.

Wednesday: Partly cloudy. Chance of morning fog. Mostly sunny afternoon. Light winds becoming northeasterly 15 to 25 km/h during the day then tending northerly during the evening. Min 15, Max 27.

Thursday: Late shower or two. Mostly sunny morning. Medium chance of showers in the afternoon and evening. Light winds becoming southeasterly 15 to 25 km/h during the afternoon. Min 16, Max 29.

Tuesday: Mostly sunny. Light winds becoming northeasterly 15 to 25 km/h in the early afternoon then tending northerly 15 to 20 km/h in the evening. Min 15, Max 25.

Wednesday: Late shower or two. Cloudy. Medium chance of showers, most likely in the evening. Winds north to northwesterly 25 to 35 km/h turning west to southwesterly 15 to 20 km/h during the evening. Min 17, Max 30.

Thursday: Showers. Windy. Winds southerly 25 to 35 km/h increasing to 25 to 40 km/h during the morning. Min 12, Max 18.

Tuesday: Partly cloudy. The chance of fog in the early morning. Light winds becoming northwesterly 15 to 25 km/h in the middle of the day then becoming light in the evening. Min 5, Max 24.

Wednesday: Showers. High chance of showers, most likely in the afternoon and evening. Winds northwesterly 25 to 35 km/h becoming light during the evening. Min 8, Max 21.

Thursday: Partly cloudy. High chance of showers, most likely in the morning. Winds southerly 15 to 20 km/h tending southeasterly during the morning then becoming light during the evening. Min 3, Max 17.

Tuesday: Cloudy. The chance of fog in the southeast suburbs in the early morning. Slight chance of a shower in the late afternoon and evening. Light winds becoming north to northwesterly 20 to 30 km/h in the morning then becoming light in the late afternoon. Min, 11, Max 23.

Wednesday: Rain, easing later. Very high chance of rain, most likely in the morning and afternoon. Possible small hail in the evening. Light winds becoming southwesterly 20 to 30 km/h during the morning. Min 11, Max 15.

Thursday: Cloudy. Slight chance of a shower. Winds southwesterly 20 to 30 km/h tending southerly during the day then becoming light during the evening. Min 8, Max 14.

Tuesday: Cloudy. The chance of frost in the east in the early morning. Slight chance of a shower. Light winds becoming north to northwesterly 15 to 25 km/h in the middle of the day. Min 4, Max 17.

Wednesday: Partly cloudy. Medium chance of showers. Winds northwesterly 20 to 30 km/h tending westerly 25 to 35 km/h during the morning. Min 9, Max 14.

Thursday: Cloudy. Slight chance of a shower in the morning and afternoon. Winds west to southwesterly 20 to 30 km/h turning northwesterly 15 to 20 km/h during the evening. Min 4, Max 13.

Tuesday: Shower or two. Cloudy. Medium chance of showers, most likely in the late afternoon and evening. Light winds becoming northwest to northeasterly 15 to 20 km/h in the middle of the day then becoming light in the late afternoon. Min 11, Max 22.

Wednesday: Cloudy. High chance of showers, most likely in the morning. Winds south to southwesterly 15 to 20 km/h increasing to 40 km/h before tending south to southeasterly 20 to 30 km/h during the day. Min 11, Max 16.

Thursday: Partly cloudy. Winds east to southeasterly 15 to 25 km/h tending south to southeasterly during the afternoon then becoming light during the evening. Min 6, Max 18.

Tuesday: Partly cloudy. Slight chance of a shower in the early morning. Winds southerly 15 to 20 km/h increasing to 30 km/h before turning southeasterly 15 to 25 km/h during the day. Min 11, Max 22.

Wednesday: Sunny. Winds east to southeasterly 15 to 25 km/h tending east to northeasterly 20 to 30 km/h during the morning then becoming light during the afternoon. Min 10, Max 25.

Thursday: Possible shower developing. Medium chance of showers in the afternoon and evening. The chance of a thunderstorm about the hills in the afternoon and evening. Winds east to northeasterly 15 to 25 km/h tending northwest to northeasterly during the morning then tending northwest to southwesterly during the afternoon. Min 15, Max 27.

Tuesday: Cloud clearing. Partly cloudy. Slight chance of a shower about the Cox Peninsula, most likely in the morning and afternoon. Near zero chance of rain elsewhere. The chance of a thunderstorm in the south. Min 25, Max 33.

Wednesday: Partly cloudy. Slight chance of a shower. Light winds becoming north to northeasterly 15 to 20 km/h during the day then becoming light during the evening. Min 25, Max 33.

Thursday: Partly cloudy. Medium chance of showers. The chance of a thunderstorm in the south. Light winds becoming northwest to northeasterly 15 to 20 km/h during the afternoon then becoming light during the evening. Min 25, Max 33.