ANOTHER spell of dangerous bushfire conditions begins in Victoria on Thursday, with a total fire ban declared for the northwest of the state.

But a greater threat looms on Friday, when a code red catastrophic bushfire warning has been issued for the Mallee and northern country regions.

The total fire ban came into effect for 24 hours from midnight (AEDT) and covers a range of towns including Mildura, Swan Hill, Ouyen, Bendigo and Horsham.

Country Fire Authority state controller Russell Rees said the Bureau of Meteorology has indicated extreme conditions predicted for the Mallee and northern country districts on Friday could also extend to the northeast.

"Given today's bureau forecasts for Friday are for code red conditions in the Mallee and the northern country, we are advising people in these two districts to prepare early,'' Mr Rees said.

He said residents in bushfire-prone areas need to activate their fire plan and monitor the district fire danger ratings and daily weather forecasts on the CFA website and in the media.

"If you live in a high-risk area and your plan is to leave, the safest option is to leave the night before or early in the day, on a day when the Fire Danger Rating is Code Red in your district,'' Mr Rees said.

He said that on a code red day people can't be sure they will be able to defend their homes.

Fires can spread quickly when winds are strong and you need to know in advance what you are going to do if faced with a fire,'' he said.

"It is too late to decide when you see smoke or flames.''

Departments of Sustainability and Environment chief fire officer Ewan Waller said anyone planning to travel in bushfire-prone areas are reminded that the bush is not a safe place to be.

He said parks and forests in districts with a fire danger rating of code red will be closed as a public safety measure.