(CNN)Rescue teams resumed their search on Sunday for a University of Washington professor who recently went missing during a hiking trip.
Sam Dubal, 33, left for Mount Rainier National Park on October 9 and was supposed to return the next day. He was reported missing on October 12 after he didn't come home, and rescue teams have been trying to find him since.
For the first nine days, a group including park rangers, volunteer hikers and helicopter crews from the National Park Service and US Air Force searched for Dubal on the ground and by air. But poor weather on October 21 and 22 limited the abilities of rescuers to continue searching on the ground.
Dubal's family started a petition on October 22 pleading that rescue teams continue searching for him aggressively for at least 72 more hours. The National Parks Service (NPS) announced on Sunday that teams had resumed the search for Dubal on the ground.
"We cannot bear the thought of an abandoned Sam during a survivable period along with improving weather and with the very best of search teams in charge," his sister Dena Dubal told CNN in an email last week.
The area of Mount Rainier National Park where teams are searching for Dubal ranges from 2,000 to 5,000 feet in elevation and includes dense forests, rocky terrain, subalpine meadows and bodies of water, NPS said in a news release.
Recent winter storms have covered much of that area with snow, while temperatures have dropped below freezing even at lower elevations, NPS said. And just a day after Dubal set out for his hike, a storm washed out the crossing he would have used to traverse the Carbon River, according to the release.
Helicopter crews searching for remains on October 22 didn't find a body, Dena Dubal said last week. At the time, she said the family believed there was a high chance Sam could still be alive given his hiking experience and the gear he was carrying.
Sam Dubal is 5' 9" and 155 pounds, has black hair and a short black beard and is possibly wearing a blue jacket.
Mt. Rainier sees record number of searches
There have been a record 60 searches at Mount Rainier National Park this year, NPS said in a news release.
One hiker is still missing, and one mountaineer who was found dead couldn't be recovered because of dangerous icefall conditions, the agency said.
Numerous people are reported missing from national parks each year, although there's no official count.
A 2018 article in Outside magazine reported that at least 1,600 people remain missing from public lands under mysterious circumstances, and the National Parks Service currently lists 23 people on its website who went missing from national parks and whose cases are unresolved.
Wandering off trail is the most common reason that hikers get lost, according to a study by SmokyMountains.com. Whether or not a person survives depends largely on their ability to find food, shelter, water and warmth, though extreme conditions in the wilderness can make that challenging.
When embarking on a trip in the wild, experts recommend packing essential equipment, including maps, fire starters and extra layers of clothing. If venturing off route, hikers should identify a "bailout direction," such as a creek or road and leave a trail as they go.