Rainfall forecast across the state tomorrow afternoon and night should extinguish fears of a repeat of the catastrophic heatwave conditions of February 7, 2009, that triggered Australia's worst-ever bushfires.

The toll of 173 human lives, thousands of dead livestock and wildlife, 2029 destroyed homes and 4500 square kilometres of scorched land will be remembered in ceremonies across the state, including the south-west.

Bureau of Meteorology forecaster Dean Stewart yesterday said the south-west should receive between 10mm and 20mm of rain with thunderstorms delivering heavier falls in localised areas.

Mr Stewart said the rain band would sweep through in the afternoon and clear the next morning, bringing cool weekend weather.

Country Fire Authority operations manager for region six, Brian Brady, said the forecast indicated falls could be as much as 50mm in some areas.

"At this time of the year this sort of rainfall will give us an extra week or two of relief from extreme fire danger," he said.

"It will dampen things in the bush and put moisture in grassland. Conditions will certainly be much better than this time last year."

His counterpart in region five to the west, Mick Harris, said the rain would be a welcome lead-in to the Black Saturday anniversary.

"The lasting effectiveness of the rain depends on what weather follows next week," he said.

"Hopefully the thunderstorm lightning will be accompanied by rain."

CFA representatives will join community members for a commemorative barbecue at Coleraine on Sunday to recall the horror hours when fire swept through about 1000 hectares on the edge of the town. One person was badly burnt and one house destroyed.

Firefighters saved six other houses, including the home of the parents of Premier John Brumby.

Mr Harris said the fire season so far this summer had been mild. He attributed this partly to vigilance by the public and the CFA putting more resources into bringing fires under control quicker.