Today will be cloudy across the south-west with a top temperature in Warrnambool of 22 degrees.
There's a 60 per cent chance of showers, most likely during the morning and afternoon.
Winds will be north-westerly 20 to 30 km/h.
A high pressure ridge extends across southern Victoria from the Bight.
The ridge will weaken today as a cold front develops in the Bight, with the front forecast to cross Victoria on Tuesday as an intense low forms near western Tasmania then moves south.
A new ridge of high pressure in then expected to develop in its wake on Wednesday, remaining over inland Victoria during Thursday as another cold front crosses Tasmania.
Hamilton is expecting a top of 23 degrees on Monday, Colac 24, Ararat 24, Casterton 23, Mortlake 23, Heywood 22, Portland 20 and Port Fairy 22.
Top temperatures expected for Warrnambool this week include 15 on Tuesday, 16 on Wednesday, 19 Thursday, 21 Friday, 22 on Saturday, 26 on Sunday and next Monday will be about 21.