An emergency warning was issued for residents near Ararat. (ABC News)
© ABC NewsAn emergency warning was issued for residents near Ararat.
Thousands of people in 28 communities are being urged to evacuate a large fire zone as an out-of-control blaze bears down on them in Victoria.

An emergency warning has been issued for the communities west of Ballarat with concerns about a wind change is expected to sweep the area between 6pm and 7.30pm.

Residents in another nine townships nearby have also been advised to leave.

Conditions are not expected to ease until about midnight, Victorian Country Fire Authority chief officer, Jason Heffernan, told reporters on Thursday afternoon.

He said 1,000 firefighters were attempting to control the fire along Bayindeen-Rocky Road that ignited in bushland and "rapidly took off".

No properties have yet been reported as damaged.

"I'm here to tell communities the fire situation will get worse before it gets better," Heffernan said.

The Western Highway was closed in both directions between Ballarat and Ararat, with diversions set up using the Sunraysia Highway and Pyrenees Highway via Avoca.

People in the fire area have been urged to head east towards Ballarat, where a relief centre has been set up at a sports reserve in the suburb of Wendouree with another centre open at Ararat.

Victorian premier, Jacinta Allan, said spot fires had started hundreds of metres ahead of the fire front and urged people to stay on top of emergency alerts.

"This is a fire situation that is continuing to evolve very quickly and there will be ongoing updates both to the broader Victorian community but particularly, too, to people in the local area as this fire continues to move," she said.

V/Line services on the Ararat Line and 11 bus routes have been suspended but no school closures are expected on Friday.

At a snap press conference on Thursday afternoon, Allan said the out-of-control fire was cause for "grave concern".

"With hot winds and predicted thunderstorms this evening with the wind change, it's going to continue to be a difficult few hours ahead," she said

She said about 1,000 firefighters were on the ground - supported by 24 aircraft and 100 vehicles - battling the blaze, while 16,000 emergency alerts had been sent to mobile phones and landlines in the affected area.

Langi Kal Kal Prison is located near the fire and its emergency response plan has been activated, emergency minister, Jaclyn Symes, said.

She said prisoners with health conditions exacerbated by smoke had been moved and the facility's general manager would work with authorities over the health of prisoners and staff.

More than 2,100 customers were left without power due to the conditions and a further 600 are still without electricity after storms last week, the state government said on Thursday evening.

29 students from schools in Beaufort and 31 patients from the town's hospital have been taken to Ballarat.

Heffernan urged anyone driving in Melbourne to give way to fire trucks heading towards the blaze.

A week after bushfires and storms razed properties and left half a million homes and businesses in the dark, parts of the state recorded temperatures of more than 40C through Thursday. Storms are expected to bring 80km/h winds and dry lightning in the afternoon.

Extreme fire warnings have been also issued in South Australia, Tasmania and Western Australia, where emergency services have been fighting blazes since early summer.

A watch and act warning is in place for a bushfire in central Tasmania, with emergency services urging those nearby to prepare to leave.

Last week, bushfires in the Grampians national park destroyed 46 properties and razed more than 6,000 hectares (14,800 acres) of bush and farmland.

In the east, wind gusts of up to 130km/h levelled major power lines and transmission infrastructure, cutting power to 530,000 homes and businesses and leaving 37 homes uninhabitable.

While fire risks across the country are expected to decline over the coming days, the Bureau of Meteorology expected severe storms to hit south-eastern New South Wales with damaging hail and winds on Friday.