evidence: The weather and climate of Mount Everest is one of extremes. Temperatures at the summit are never above freezing and during January temperatures can drop as low as -60° C (-76° F). Despite the low temperatures the biggest issue faced by climbers are hurricane force winds and wind chill. When the jet stream dips south during the winter hurricane force winds may develop reaching more than 285 km/h (177 mph). These winds relax in the month of May and most climbers try to attempt the peak during this short window. [...] 1. Winter Weather at Everest: Winter weather (Nov to Feb) is dominated by the southward migration of the northern hemisphere jet stream which brings high winds, cold temperatures and on occasion heavy snow falls. Winter can be a great time for trekking as the crowds trying to avoid the cold clear out. Day temperatures are comfortable and sunny skies generally prevail although it can get well below freezing at night. [...] Wind chill and low temperatures combined with high elevation make the summit of Everest one of the least hospitable places on the planet during the winter. The adjusted wind chill temperatures of 70C (-90F) observed on the summit compare to the worlds coldest places such the record cold -67.8C (-90F) in Siberia and -89C (129F) measured at Vostok in Antarctica.