Historically October 7 and 9 were the top Everest autumn summit days and here is why.
Diving into weather stats 10 years ago we isolated a brief period during autumn ideal for an Everest summit push. Kuriki is aiming his summit push right at that “autumn weather window”. Here is the article from 2003, unearthed from our archives:
Something happens around October 10
Weather is a very crucial part of climbing – it can make or break a summit. Everest climbers are constantly looking to the sky and reading the forecasts in hopes identifying the elusive ‘weather window’ – a period of good weather that allows for a summit push.
For the past several seasons, ExplorersWeb and AdventureWeather have been compiling weather forecasts throughout the Everest seasons and analyzing them.
AdventureWeather has just been updated today with two new charts analyzing the weather of the 2001 and 2002 fall Everest seasons (follow the links to the left for an enlarged view). Both years, it is very clear that around October tenth, two things happen:
1. The wind speed increases dramatically and for the most part stays that way through the end of October.
2. The humidity level drops off considerably and stays down as well.
The Monsoonal flip-flop
As the monsoon recedes, the humidity decreases and the wind picks up. This is the exact opposite as in the spring when the arrival of the monsoon means lower winds speeds and more precip. The arrival of the monsoon also brings with it a period of good weather as the transition occurs.
Also included on these charts are historical summit data for Everest. A majority of the summits occur in early October, with the bulk of them happening between the 5th and the 10th. In the later 2/3rds of the month, summits drop off considerably.
A fall weather window?
Could the second week of October be the fall’s weather window? Maybe or maybe not. This past spring, the monsoon came rather late and a weather window showed itself towards the very end of the season. Could the monsoon leave the area late as well this Fall? Sure, just as much as it could come early.
Though it might be uncertain when this window will appear, there is a degree of certainty that it will come, just as there is a degree of certainty that the monsoon will come and go with the seasons. Weather prediction is not an exact science, but the knowledge that a window may exist in the fall and an idea of when it might occur is in itself very useful information for teams climbing. Just as teams in the spring try to be ready in early May, teams in the fall might aim to be ready by early October in anticipation of a break in the weather.
