A tourist carrying a "very limited water supply" has been found dead in the Australian Outback, where temperatures have been exceeding 40 degrees.

The 33-year-old man, from California, was walking the Larapinta Trail, west of Alice Springs, with a 40-year-old companion.

They set out on a 16km trek to the summit of Mount Sonder on Wednesday morning, police said.

His companion said he took a wrong turn as he ran ahead during their descent.

A search party found the man's body at the base of the mountain three hours later.

While police have not revealed cause of death, they said it was not suspicious. A coroner will investigate. The man's identity has not been made public.

"Heat and exposure were contributing factors. The gentleman had a very limited water supply," Sergeant Michael Potts said.

The temperature reached 42C (108F) at Alice Springs on Wednesday.

The semi-desert area has little shade or water.