Australians are holding a national day of mourning today for the 173 people who died a year earlier in the country's worst wildfire disaster.

Almost a year after the Black Saturday bushfires devastated Victoria, two teenage boys have been charged with lighting the Bendigo blaze.

A cool southwesterly change is moving across Victoria, reducing the catastrophic fire risk that has forced people from homes and campsites.

Australia is cooling down after another day of deadly heat with temperatures in three states soaring into the 40s, including record highs in Melbourne.

A long spell of dry weather is likely to lead to more fire bans being put in place.