He parked at Otaki Forks on Tuesday, headed for Kime Hut. His planned route included Renata Ridge and Waiotaru Rd.
However, the man has not contacted anyone since he started his solo tramp and police are now concerned for his safety.
He is believed to well-prepared for a short stay, is fit and experienced.
The temperature at Tararua Forest Park is currently 3 degrees. But factoring in wind chill, temperatures at Kime Hut are expected to fall to -7 degrees tonight. MetService has predicted the area will stay mostly dry, but the odd shower is possible.
Palmerston North police want to hear from anyone who visited the park this week, particularly if they had been near Kime Hut, Elder Hut and Otaki Forks.
Police described the man as Caucasian, tall and of lean build, balding with short grey hair.
Anyone with information can contact police on 06 351 2535