Mt. Washington Observatory, January 1933 (Photo courtesy of the Boston Public Library, Leslie Jones Collection)

In 1870, a scientific expedition involving the first wintertime occupation of Mount Washington’s summit led to the establishment in May 1871 of a year-round weather observatory.

The observatory is a private, nonprofit scientific and educational institution organized under the laws of the state of New Hampshire. The weather observation station is located on the summit of Mount Washington. The observatory’s mission is to advance understanding of the natural systems that create the Earth’s weather and climate, by maintaining its mountaintop weather station, conducting research and educational programs and interpreting the heritage of the Mount Washington region.

The first regular meteorological observations on Mount Washington were conducted by the U.S. Signal Service, a precursor of the Weather Bureau, from 1870 to 1892. The Mount Washington station was the first of its kind in the world, setting an example followed in many other countries.

The Signal Service occupied the summit and kept records from 1870 to 1892. Starting in 1932, the current observatory began keeping records. In 1934, the observatory recorded a wind gust that at the time was the highest recorded wind speed in the world, a record that was held until 1996. The observatory’s weather data have accumulated into a valuable climate record since. Temperature and humidity readings have been collected using a sling psychrometer, a simple device containing two mercury thermometers. Where most unstaffed weather stations have undergone technology upgrades, consistent use of the sling psychrometer has helped provide scientific precision to the Mount Washington climate record.

The observatory makes prominent use of the slogan “Home of the World’s Worst Weather,” a claim that originated with a 1940 article by Charles Brooks (the man generally given the majority of credit for creating the Mount Washington Observatory), titled “The Worst Weather In the World” (even though the article concluded that Mt. Washington most likely did not have the world’s worst weather).

The Sherman Adams summit building, named for the 67th governor of New Hampshire, houses the observatory; it is closed to the public during the winter and hikers are not allowed inside the building except for emergencies and pre-arranged guided tours.

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