Truly the most outstanding feature of Mount Washington is its weather, considered by many to be the "worst in the world". The highest wind velocity ever measured on earth, 231 miles per hour, was clocked on the summit on April 12, 1934. Wind exceeds hurricane force (75 mph) over one hundred days a year. An average wind velocity of 35 mph, coupled with an average temperature of 27.1 F (-2.7C) makes for extreme wind chill conditions.

Why is the weather so severe? In addition to its lofty elevation, Mount Washington lies in the path of both the major storm tracks and the air mass routes that affect the Northeast. The mountain's topography and high elevation create an accelleration effect on the wind in much the same way a river's velocity increases as it passes over a rapid.

Because the summit provides a model vantage point for weather, it is an ideal location for the Mount Washington Observatory, a private, non-profit corporation that conducts weather observations and scientific research. A museum and gift shop for visitors is operated by the Observatory, and pre-scheduled tours of the weather station are offered. The Observatory is staffed throughout the year, including winter, when access to the summit is both limited and dangerous.