(CNN) -- Three experienced hikers were rescued from California's Mount Whitney, but a father and son in a separate group are missing, the National Park Service said.
Battling heavy snow, rescue personnel and a California National Guard helicopter reached the three men around noon (3 p.m. ET) Thursday.
The men were part of a group of 10 hikers who set out on their journey up the mountain on Monday.
About 45 people looked for the three hikers -- Phillip Michael Abraham, 34; Dale Clymens, 45, and Stevan James Filips, 45 -- the National Park Service said in a statement.
All three were able to walk and move during a general health assessment.
Two other hikers on a 36-mile cross-country loop were supposed to return Tuesday.
They are Sinh Baghsohi, 27, and his father, whose first name is unknown, park officials said. Both men are originally from Iran, but their current residences are not known. The younger Baghsohi is 6 feet, 5 inches tall and weighs about 287 pounds. His father is 6 feet tall and weighs 180 pounds.
They had hiked in with a friend, who became ill and hiked out, the park service said.
Dave Paladino, an Omaha, Nebraska, resident and leader of the larger group, said extreme weather dumped up to three feet of snow and drastically lowered visibility in Sequoia and Kings Canyon national parks.
The group of 10 hikers shared a love of climbing, outdoor activities and adventure, Paladino said.
They set out on their hike shortly after 4 a.m. Monday in several sub-groups, including one led by Paladino and another including all three missing hikers.
"Every single one had been training for this event for years," said Paladino.
The snow began for Paladino's group when they reached 10,000 feet up what he called the "10-mile hill," and picked up significantly as they went up another 2,000 feet. His group reached the summit around 3:30 p.m. Monday, staying briefly at a shelter there before going back down the mountain.
The climb back down was much more difficult than expected, according to Paladino, due to the heavy snow.
"It was by far the hardest thing we've ever done," said Paladino, who said he has climbed Mount Rainier in Washington state, among other peaks.
At one point, his group met and talked briefly with the climbers who later went missing. Abraham later sent several texts, the last of which was between 4 a.m. and 6 a.m. Tuesday in which they said they couldn't find the trail because of the snow and were heading to the summit shelter.
The three climbers did not have snow shoes, said Paladino. However, they likely had enough food and water to last several days, he said. Temperatures near the mountain's peak were in the 20s, Paladino added, not low enough to make frostbite a major concern.
A rescue operation involving two hikers was begun and aborted Wednesday because of the snow. On Thursday morning, "bigger and more experienced teams" were brought in, said Paladino.
"We wanted to do this," said Paladino. "These guys were doing what they loved, and we'll continue to do what we love."