The weather climate Everest base camp is very chilly. And it is never above the level of freezing on the summit. During the December- January the temperature drop down more than -350 C at the Base Camp. And cross the -500 C at the top. Despite the low-temperature climbers also face the problems of winds.
From March to May and September to November is a moderate weather for trekking and also for climbing. As geographical view Mt. Everest lies in 280 north of equator and influences with Indian monsoon that brings bring the clouds and rain from June to early September.
Winter season is cold but clear weather and also better trip to escape from crowded. Generally, the day time is comfortable, sunny days but midnight is cold. Some time winter season brings heavy snowfalls too. Overall trekking up to Everest Base Camp is good even in winter.
Spring season is an ideal time for Trekking, lots of trekkers are found in T-Shirt during the day time. It sunny and also sometimes rainy.
Monsoon season is not the good time for Trekking in Everest. Frequently rainfalls and most days are cloudy.
Autumn is a perfect for trekking, it is a comfortable time. The days are more clear. You can see the awesome views of valleys, mountains, lakes and glaciers.
Autumn is best for trekking and April- May is best for expeditions.