Unlike the failed predictions for a downpour last weekend the Bureau of Meteorology is confident its forecast for today and tomorrow will be on the mark.

A severe weather warning for heavy rainfall was issued for the South-West, Mallee, Wimmera, Northern Country, North Central, North East and Central forecast districts on Monday afternoon. 

"It's a different scenario to last week when the moisture didn't develop over the south, but pushed across NSW," bureau senior forecaster Dean Stewart told The Standard on Monday.

"As day breaks it should be raining in the south-west.

"We are predicting moderate to heavy falls across western Victoria and even heavier rain across the Wimmera and central areas."

Mr Stewart said a trough was developing Monday across South Australia lifting moisture from the atmosphere including tropical moisture from the Northern Territory, western Queensland and western NSW.

Thunderstorms are also tipped to bring heavier falls to parts of the region.

Wednesday  the rain is likely to ease with passing showers producing less than 5mm before a dry latter part of the week.

The timeline on Weatherzone webpage shows heavy rain from 6am as winds switch to the north-east before swinging to the west mid-afternoon with temperatures remaining around 20 degrees.