Two climbers are awaiting rescue near Denali’s peak, a day after requesting help following their summit of North America’s tallest mountain during peak mountaineering season, according to officials at Denali National Park and Preserve.

A third climber, rescued late Tuesday, and the other two, who are hypothermic, all have experience on high-elevation international peaks, including previous climbs on Denali, said park spokesperson Paul Ollig.

Rangers received an SOS from the climbers at 1 a.m. Tuesday, reporting hypothermia and inability to descend from the 20,310-foot summit. They communicated until 3:30 a.m., planning to move to the “Football Field” at 19,600 feet. Communication ceased afterward, and their satellite device location remained unchanged.

Cloud cover initially grounded the park’s high-altitude helicopter. The Alaska Rescue Coordination Center then deployed an HC-130J from Anchorage to assist. By noon, two climbers were located between 19,000 and 20,000 feet, while the third was seen at 18,600 feet.

Clearing conditions allowed a helicopter to reach a 14,200-foot camp Tuesday evening, where rangers were treating frostbitten climbers from another expedition. These climbers were evacuated to Talkeetna.

A further attempt to rescue the distressed climbers Tuesday night succeeded in reaching one, found at a 17,200-foot camp with severe frostbite and hypothermia. Aided by a guided party until the park team arrived, this climber was flown off the mountain and later medevaced from Talkeetna.

An experienced guide on the upper mountain assisted the remaining two climbers at the “Football Field” but had to descend to 17,200 feet for safety due to worsening conditions.

Rescue efforts on Wednesday were thwarted by clouds and wind, preventing aircraft or ascents. Rescuers await improved conditions to continue attempts.

The climbers likely have minimal survival equipment, said Ollig, as teams often ascend lighter on summit day for speed.

Despite the dramatic nature of the rescue, it is not considered extraordinary. Currently, 506 climbers are attempting to summit Denali, with Memorial Day weekend marking the busiest part of the climbing season. So far, 117 climbers have completed their attempts, with 17 reaching the summit.

Denali National Park and Preserve is about 240 miles north of Anchorage.