Search dogs have been called in to help teams of Police and LandSAR volunteers looking for a hunter missing in the Blue Mountains northwest of Balclutha.
The man was understood to be wearing thermals, trousers, a rainproof jacket, beanie and gloves. He also had a backpack with a basic first aid kit and a thermal blanket.
Efforts to locate the man using the helicopter's night-vision equipment have so far been unsuccessful, and the helicopter has been stood down for now.
The search continues in what are cold and drizzly conditions.