Hot and sunny across the south-west, Warrnambool's top tipped to be 39 degrees

Winds will be north to north-easterly and light tending north to north-westerly 20 to 30 km/h during the morning then becoming even lighter in the evening.

Warrnambool is expecting a top temperature of 39 degrees, Hamilton 39, Colac 37, Ararat 37, Casterton 41, Mortlake 40, Heywood 39, Portland 39, Port Fairy 39, Terang 38 and Camperdown 37.

For summer in Victoria, Bureau of Meteorology senior climatologist Blair Trewin said there was a "persistent and extreme heat", particularly in December and January.

"Averaged over the state its the hottest summer on record," Dr Trewin said.

"It's the first time ever in Melbourne where we've had a summer without a day below 19C," he said.

Specific highlights of the summer temperatures across the south-west are now being research by BOM staff.

Currently there is high pressure system will be centred over the Tasman Sea for the next few days.

A weak low pressure trough will reach far south-west Victoria later on Saturday before drifting through most of the state on Sunday.

The trough will stall over eastern Victoria Sunday night before lingering near north-eastern Victoria on Monday, as a weak ridge extends from the Bight towards southern Victoria. 

On Saturday Warrnambool is likely to have a top of 36 degrees before reaching 27 on Sunday.

But, the BOM did tip Warrnambool's top on Thursday would be 33 degrees and it got to 39 at 1.35pm.

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