"The Weather Window is a period with no Jetwind, low general winds and little precipitation perfect for climbing above 8000 meters. According to historical data the majority of all successful Everest summits occur during the Weather Window that traditionally occurs between approximately May 15 and June 8, when the Monsoon hits the Himalayas. The climbing season as defined by the Nepal government climbing permits normally ends June 1, except that this season various expeditions have 75 day permits which go through mid June. The length of the Weather Window is approximately 2 weeks. The Weather Window might be disrupted by incoming weather systems."