Thunderstorms, rain, hail to lash Victoria

Victorians are being told to brace for a low-pressure system which will bring rain, hail and thunderstorms.

Heavy rain is expected to lash parts of Victoria on Thursday, forecasters say. (AAP)

A month's worth of rain is expected to crash down on Victoria in one day, as people are being warned to brace for wild weather.

The wrath of tropical cyclone Owen will be dragged into a low-pressure system forming over Victoria on Thursday.

The Bureau of Meteorology warns there will be heavy rain, thunderstorms and damaging to destructive winds associated with tropical cyclone Owen.

The low-pressure system is expected to dump between 50 and 100mm of rain in Victoria's northeast and central areas, including Melbourne, depending on thunderstorm activity.

Other areas are forecast to have between 30 to 50mm on Thursday.

It is due to bring the average December rainfall in one hit.

Hail stones about 2cm in size could fall as damaging winds with gusts up to 90km/h sweep through the warning areas.