Dust storms, muddy rain and flash flooding could hit Victoria again as blazing heat brings another spike in the fire risk.

Melbourne will be more like Darwin on Friday with oppressive humidity and a top of 43 degrees, Bureau of Meteorology forecaster Diana Eadie said.

Melburnians will wake to hot, dry weather on Friday morning, before northerly winds make it humid and sticky.

Those winds will pick up dust from the state's north-west that could arrive in the city with localised rain, making it likely there will again be a downpour of red, muddy rain.