A supplied image of an arial view of the Little Desert bushifre in Victoria [Source: AAP Image/Supplied by State Control Centre]

Raging bushfires at either end of a blaze-ravaged national park could merge as crews grapple with the rugged terrain and southerly winds.

With locals in the northwest Victoria town of Dimboola returning home after a fast-moving bushfire destroyed property, authorities are shifting their focus to two out-of-control blazes in the popular Grampians National Park.

The fire to the southwest of the park has grown to 4500 hectares and is threatening isolated properties and camp grounds.

Residents and holidaymakers in the area were urged to leave late on Tuesday, with roads leading to Halls Gap still open.

State Control Centre spokesperson Luke Heagerty said it grew considerably in the past 24 hours and was sending smoke towards the regional centre of Horsham and into NSW.

Further north, a collection of smaller fires, ranging from 150ha to 300ha, are burning in the Wallaby Rocks area near Zumsteins.

Firefighters are working on protecting private farmland next to the park ahead of forecast warmer, windier weather later in the week and into next week.

“Once the fire has reached the end of the park and it’s in more open grassland, we can have fire crews there waiting to extinguish and to also establish some containment lines if possible,” he told AAP on Wednesday morning.

It took 21 days to bring blazes in the Grampians, sparked on December 17, under control.

Forest Fire Management Victoria chief fire officer Chris Hardman said the latest blazes could burn for weeks, while Mr Heagerty conceded they could join.

“Where we’ve got the right combination of wind and where we’ve not been able to establish containment lines or use some other strategies to slow the spread of the fire, that is a possibility,” he told AAP.

“We really don’t want to use that as an assumption that that will happen but the reality that we’re dealing with in the Grampians National Park is that it’s very difficult to get crews in to the area between those two groups of fires.”

It was a wind change that left locals in Dimboola, near the South Australian border, just 30 minutes to pack up their lives and evacuate over fears the town was under threat.

The blaze was sparked by dry lightning, one of 10,000-odd strikes that hit the ground in the state on Monday, and has grown to almost 70,000ha.

“It all sort of hit in a two hour period, so quite a distance away, obviously you see the plumes,” cattle owner Quentin Barrett told AAP.

“We thought we’re good, we thought it might miss us, but then the wind just changed and everything just ran.”

A wedding venue and two farm houses were destroyed in the Dimboola fire, which is not yet controlled but has been downgraded to watch and act with locals allowed to go home.

Mr Barrett lost three cattle when flames jumped across a river at the back of his brother’s property and tore through fences.

“One fence line could cost upwards of $10,000 to $20,000 for a stretch, and there’s three of those,” he said.

“We unfortunately weren’t insured.”

Dimboola resident Bree Myers and seven-year-old daughter Indie Francis hung a sheet painted with the words “thank you fireys” outside their house the moment they returned.

“We were just really worried, seriously worried, that we’d come back to nothing,” Ms Myers said.

“It’s the least we could do, just so they know that we appreciate it.”