Everest’s environment is forever hostile to living creatures. On the top, the warmest average daily Mount Everest temperature (in July) is just around −19 ° C (−2 ° F). In January, the coldest month, peak temperatures average −36 ° C (−33 ° F) and can drop to −60 ° C (−76 ° F).
During the summer monsoon, Mount Everest temperature is relaxed. Precipitation falls as snow (late May until mid-September). On Everest, the chance of frostbite is extremely high for climbers.
In the spring months of April and May, temperatures warm rapidly bringing t-shirt weather while nights are still cool and chilly. In this time period, it is not unusual to see climbers wearing t-shirts all the way up to camp 3.
Storms can suddenly pop up, and Mount Everest Temperature can suddenly plunge. During the winter hurricane-force winds can build to over 285 km/h (177 mph) when the jet stream dips south.
Those winds relax in May and during this short window, most climbers try to make it to the peak. Given the low Mount Everest temperatures, hurricane-force winds and wind chill are the main challenges faced by climbers.
From 15th December until the end of January, the coldest temperatures of the year occur with temperatures at the summit averaging -37°C (-35F) while those at Everest Base Camp average -17°C (1.4°F).
The Everest peak is so high that it approaches the lower limit of the jet stream, and it can be buffeted by more than 100 miles (160 km) of sustained winds per hour.
Everest lies at the edge of the Indian Monsoons effect that brings moisture and clouds between June and September. The cold months are December/January and between these two seasons is the best trekking.