Melburnians could be in for our biggest 24-hour period of rainfall for the year overnight, with the Bureau of Meteorology predicting heavy rain from 10pm on Thursday and continuing until 9am Friday. The heaviest rain will set in around midnight.

The bureau is expecting 15 to 35 millimetres of rain to hit Melbourne and parts of Victoria as a vigorous cold front makes its way across the state from the south-west. Melbourne's highest daily rainfall for the year so far is 11 millimetres.

Bureau of Meteorology senior forecaster Richard Carlyon says there's a possibility of isolated flooding in Melbourne and parts of central and northern Victoria.

"Given the autumn period ... there could be blockages due to leaves," Carlyon says. "So even though it's not a huge fall – we're not talking about high rainfall rates, it's fairy steady rates – there could be some flash flooding."

Temperatures are forecast to drop across the state, with a 14-degree high expected for Melbourne on Friday and most other areas around Victoria predicted to reach no more than 15 degrees.

A strong-wind warning has also been issued for coastal areas west of Lakes Entrance. The bureau and Vicroads also warn drivers never to attempt to cross flood waters.