Five climbers are attempting to scale Mount Everest, battling extreme cold, high winds and piled-up snow and ice as they try to become the first to reach the top of the world’s highest mountain in the winter in 27 years, an official said Wednesday.

The climbers — three from Spain and two from Germany — are already acclimatizing around Everest’s base camp area as they wait for weather conditions to improve, said Meera Acharya of Nepal’s Department of Mountaineering.

They’re expected to be accompanied on their ascent by Nepalese Sherpa guides, but it was not yet decided how many would go up the slope with them.

While there are no rules prohibiting climbers from attempting to scale Everest during the winter, only a handful have reached the mountain’s 8,850-meter (29,035-foot) -high peak during that season. The feat was first accomplished in 1980, and has not been done since 1993.

Everest is mainly scaled during the spring climbing season in April and May, when weather conditions are favorable.