Police and State Emergency Service members are on Thursday searching bushland and tracks, while the air wing takes to the sky around the Thomson Dam in West Gippsland in hope of finding Caleb Forbes, 22, and Shannon Lowden, 21.

The couple set off on a camping trip on Friday, and the alarm was raised when Mr Forbes failed to show for work on Sunday.

Inspector Shane Cashman said their disappearance was "totally out-of-character".

"If they are in their car and they've got camping gear that can keep them warm we are hopeful that they will be okay," Insp Cashman told 3AW.

"If they have moved away from their car then that's a concern but if they have stayed with their car, they can access water, they should have some supplies that have almost diminished but the water will keep them going."

Off-road motorbike riders are expected to tackle hard-to-reach terrain in hope of finding the pair or Mr Forbes' green 1994 Nissan Patrol on Thursday.

The wagon may have become bogged, snowed in, inoperable due to a mechanical fault or gone off-road, he said.

The temperature in the area may have dropped to as low as 2.5C overnight, the weather bureau said.

Ms Lowden's mother Debbie Lowden is hopeful she will find her daughter alive and well.

"I feel like they've obviously got stuck somewhere and they can't get out," she told reporters on Wednesday.

"We will be here until we find them."

Australian Associated Press