Warm and windy weather will cause very high fire danger ratings in parts of southern Australia today.

Today's warm weather is being caused by a typical spring pattern of blustery northerly winds developing ahead of an approaching low pressure trough and cold front.

Temperatures are forecast to reach 5-10 degrees above average in parts of South Australia, Victoria and western NSW on Friday afternoon, with many areas likely to have their warmest day since early autumn.

Mildura's forecast of 35 degrees would be the northern Victorian town's warmest day in six months and 11 degrees above average for October. Melbourne (29C), Geelong (29C), Broken Hill (34C), Deniliquin (30C) and Clare (29C) are also forecast to have their warmest day since April on Friday.

Very high fire danger has been forecast in five districts of South Australia and the Mallee in Victoria. A severe weather warning for damaging winds is also in place for parts South Australia today, including Adelaide and the Mt Lofty Ranges.

A windy southwesterly change will sweep across most of South Australia on Friday afternoon and evening, then cross Victoria, Tasmania and far western NSW overnight into Saturday morning. Temperatures will drop by about 10 degrees in the wake of this change for many areas.

Visit the CFA and CFS websites for the latest information on bushfires in Victoria and South Australia.