Minnesota man missing after leaving for 3-day hike in Bighorn National Forest in Wyoming: Sheriff

A Minnesota man has been missing for over one week after leaving for a three-day hike in Wyoming's Bighorn National Forest, according to the Big Horn County Sheriff's Office.

Since Friday, officials continue to search for Grant Gardner, who had planned on a three-day hike "through the Misty Moon Lake area, eventually summiting Cloud Peak," which is the highest peak within the Bighorn National Forest, the sheriff's office said in a statement on Monday.

Gardner had contacted his wife on July 29 saying he had made it to the summit, but "since that time there has not been any contact with Gardner," officials said.

As of Tuesday, Gardner remains missing, with search and rescue efforts actively continuing, officials said.

Officials discovered Gardner's vehicle in the parking lot of the West Ten Sleep trailhead -- where he began his journey -- and also learned via the hiking log at the trailhead that he had entered the area "as he had indicated in his hiking plan," officials said.

Phone records also revealed that he had reached the summit at Cloud Peak -- which is around 13,000 feet -- at approximately 7 p.m., which was concerning to officials due to the "lack of visible trails through cliffs, timber line, boulder fields and other hazards that had to be navigated after dark before reaching clear trails and safe terrain," officials said.

A text Gardner sent to his wife also indicated that the climb was "more taxing than he expected and he was tired," the sheriff's office said.

Officials said they have extensively searched for Gardner using helicopters, planes, foot teams and canines, but "conditions are extremely challenging," with at least two rescuers suffering from "medical conditions" and needing treatment.

"In addition to high altitude and terrain challenges, difficult weather patterns including winds, thunder and lightning storms have made search efforts difficult at various times of the day," officials said.

Bighorn National Forest is over 1 million acres, with 191,000 acres dedicated to the Cloud Peak Wilderness area, which is where Gardner is believed to have been traveling, according to the U.S. Forest Service.

Officials said their "hearts go out" to Gardner's family and are asking for the public's "thoughts and prayers on their behalf, and for the searchers who are risking life safety in this beautiful but unforgiving wilderness area."

The sheriff's office said updates will be provided regarding the search for Gardner "as appropriate."

Anyone who may have had contact with Gardner is urged to contact the Big Horn Sheriff's Office or the Wyoming Missing Person Tip Line.

The Big Horn County Sheriff's Office did not immediately respond to ABC News' request for comment.