FIRE crews have contained a big bushfire near Casterton, in Victoria's west, as authorities prepare for sizzling temperatures next week.

State agency commander for the Department of Sustainability and Environment Andrew Bennet said the B-Line Track blaze was contained at 4512ha.

He said crews would remain in the Casterton and Little Desert area, near the South Australia border, over the weekend to mop up and patrol the fire areas.

Mr Bennet said aircraft have been positioned across Victoria to respond to bushfires and some aircraft would be stationed in the state's west to swing into action if needed.

"There's always a concern (with the return of hot weather) and that's why we've still got resources in the area and into early next week."

He said DSE was resting crews in case they were needed.

Mr Bennet said the department was in regular contact with the Bureau of Meteorology about forecasts.

According the forecast Mildura is tipped to reach 38C tomorrow and 40C Sunday, while people in Casterton, Hamilton and Colac can expect temperatures in the high 30s tomorrow.