A total fire ban has been declared for three Victorian districts, including the Melbourne metropolitan area.

Bans are in place in the Wimmera, South West and Central districts due to warm and dry conditions on Wednesday

The Wimmera has been given a severe fire danger rating, while the rest of Victoria is under a high to very high rating.

CFA Chief Officer Steve Warrington says emergency services are on standby if any fire starts.

"Grasslands again around the west of Melbourne are a concern for us as well as the entire western corner of the state," he said.

Melbourne is forecast to reach 31C on Wednesday before a late cool change.

© AAP 2017