Uncomfortable sleep after Vic Xmas heat

Victorians will be waking up groggy and sweaty after the hottest Christmas for 18 years.

The temperature in Melbourne hit a high of 36.3C on Sunday and by 9pm it had only fallen 2C to 33.5C.

Overnight temperatures weren't looking much better, with the Bureau of Meteorology predicting a minimum of 24C.

Relief from the heat won't be in sight until Monday afternoon, with a cool change bringing showers and a possibility of thunderstorms after a high of 31C.

The heatwave will continue for the northern half of the state with temperatures expected to remain in the mid to high 30s for a number of days.

New Year's Eve is looking like a cold evening for Melburnians hoping to see the fireworks, with a top of 24C and a low of 15C predicted.