The search is still on for Jacob Rigby, an Illinois man who went missing on Sunday while hiking in Montana's Glacier National Park.

The park dispatch received a phone call at 2 a.m. on Monday saying that Rigby, 27, was overdue from a personal hike he took.

Rigby's supervisor later notified park rangers that he had not shown up for work, according to a National Park Service press release. Rigby is a seasonal worker for the Glacier National Park.

The search continues, an NPS spokesperson told the IB Times on Thursday. We haven't been able to fly today due to weather conditions.

Flathead Valley Search and Rescue and Flathead National Forest are assisting with the effort, according to the NPS.

Rigby is from Johnsburg, Illinois and attended the University of Illinois at Urbana-Champaign, according to his Facebook page.

He is described by the NPS as a skilled hiker who is familiar with the park. He is 6 feet tall and has curly brown hair. He is believed to be wearing a blue T-shirt, blue Patagonia hiking shorts, and a size 10 pair of La Sportiva boots with Vibram soles. He is possibly wearing gators, according to the NPS, and is also believed to have a white and silver Mumut daypack.