Two young children have walked away unharmed after a cold night sheltering under a tree in the Southland bush

An eight-year-old boy and 11-year-old girl have been described as being in good spirits after spending 19 hours in the wilderness.

The children had become disorientated after leaving the campground at the northern end of Mavora Lakes Rd around 2.30pm Saturday - and weren't found by rescuers until 10am yesterday.

It sparked a large-scale rescue involving up to 50 people.

Sergeant Terry Wood says the children didn't have a lot with them to keep them warm.

He says they were assessed by medics but all in all were unscathed by what happened and now have a story to tell.