Dr. Brian Carrico, 57, was spotted by a helicopter crew just before noon near Wellman Divide, high in the Mount San Jacinto wilderness.
Carrico was airlifted off the mountain and taken to the hospital by ambulance. He is said to be in good condition.
Sheriff's deputies say Carrico, an experienced outdoorsman, became disoriented in whiteout conditions Saturday afternoon. He built a snow shelter to stay warm as overnight temperatures dipped into the teens.
He also wrote "S.O.S." in the snow so he could be seen by searchers in the air.
He had last been seen Saturday morning when he went hiking above the Palm Spring Aerial Tramway. He parked his blue Audi A8 at about 10:30 a.m. Saturday in the tramway parking lot, bought a permit and took a tram to the top of the mountain.
Family members of the Redondo Beach resident contacted the State Parks department when he didn't return when he said he would.
Carrico is said to be an experienced hiker, and relatives say he was properly equipped with food, water and heavy clothing.
A number of teams took the tram up to the top of the mountain during the search. Fifteen ground teams searched the mountain in a grid-style formation, and about 70 people were up on the mountain.