The Mount Washington Observatory (MWObs) is a private, non-profit 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 in New Hampshire. 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 U.S. Signal Service, a predecessor to the Weather Bureau, 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 had the highest 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, which houses the observatory, is closed to the public during the winter and hikers are not allowed inside the building except for emergencies and pre-arranged guided tours
| Climate data for Mount Washington, elev. 6,267 ft (1,910.2 m) near the summit | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 48 (9) |
43 (6) |
54 (12) |
60 (16) |
66 (19) |
72 (22) |
71 (22) |
72 (22) |
69 (21) |
62 (17) |
52 (11) |
47 (8) |
72 (22) |
| Average high °F (°C) | 13.6 (−10.2) |
14.7 (−9.6) |
20.7 (−6.3) |
30.4 (−0.9) |
41.3 (5.2) |
50.4 (10.2) |
54.1 (12.3) |
53.3 (11.8) |
47.1 (8.4) |
36.4 (2.4) |
28.1 (−2.2) |
18.4 (−7.6) |
34.0 (1.1) |
| Daily mean °F (°C) | 4.8 (−15.1) |
6.2 (−14.3) |
12.9 (−10.6) |
23.9 (−4.5) |
35.6 (2) |
45.0 (7.2) |
49.1 (9.5) |
48.2 (9) |
41.6 (5.3) |
30.2 (−1) |
20.7 (−6.3) |
10.1 (−12.2) |
27.4 (−2.6) |
| Average low °F (°C) | −4.1 (−20.1) |
−2.4 (−19.1) |
5.0 (−15) |
17.4 (−8.1) |
29.8 (−1.2) |
39.5 (4.2) |
44.0 (6.7) |
43.0 (6.1) |
36.1 (2.3) |
24.0 (−4.4) |
13.3 (−10.4) |
1.7 (−16.8) |
20.6 (−6.3) |
| Record low °F (°C) | −47 (−44) |
−46 (−43) |
−38 (−39) |
−20 (−29) |
−2 (−19) |
8 (−13) |
24 (−4) |
20 (−7) |
9 (−13) |
−5 (−21) |
−20 (−29) |
−46 (−43) |
−47 (−44) |
| Average precipitation inches (mm) | 6.44 (163.6) |
6.77 (172) |
7.67 (194.8) |
7.44 (189) |
8.18 (207.8) |
8.40 (213.4) |
8.77 (222.8) |
8.32 (211.3) |
8.03 (204) |
9.27 (235.5) |
9.85 (250.2) |
7.73 (196.3) |
96.87 (2,460.5) |
| Average snowfall inches (cm) | 44.0 (111.8) |
40.1 (101.9) |
45.1 (114.6) |
35.6 (90.4) |
12.2 (31) |
1.0 (2.5) |
trace | 0.1 (0.3) |
2.2 (5.6) |
17.6 (44.7) |
37.8 (96) |
45.5 (115.6) |
281.2 (714.2) |
| Average precipitation days (≥ 0.01 in) | 19.7 | 17.9 | 19.0 | 17.4 | 17.4 | 16.8 | 16.5 | 15.2 | 13.9 | 16.8 | 19.1 | 20.7 | 210.4 |
| Average snowy days (≥ 0.1 in) | 19.3 | 17.3 | 16.6 | 13.1 | 6.4 | 0.9 | 0.1 | 0.2 | 1.7 | 9.1 | 14.6 | 19.2 | 118.5 |
| Mean monthly sunshine hours | 92.0 | 106.9 | 127.6 | 143.2 | 171.3 | 151.3 | 145.0 | 130.5 | 127.2 | 127.1 | 82.4 | 83.1 | 1,487.6 |
| Percent possible sunshine | 32 | 36 | 34 | 35 | 37 | 33 | 31 | 30 | 34 | 37 | 29 | 30 | 33 |
| Source #1: NOAA (normals 1981–2010, sun 1961–1990) | |||||||||||||
| Source #2: Mount Washington Observatory (extremes 1933–present) | |||||||||||||
The Observatory holds a strong tradition of education. In addition to its meteorological and research endeavors, the Observatory is involved in many educational efforts which seek to inform individuals about the many significant aspects of weather, area history, and the mountain environment. MWObs educational facilities and programs include:
The Mount Washington Observatory receives much of its support from contributing members. However, over the years the MWObs has also come to receive support from several company and organizational partners, including L.L. Bean, Eastern Mountain Sports (EMS), Cranmore Mountain Resort, the Mt. Washington Auto Road, and the Mt. Washington Valley Chamber of Commerce. In 2011, EMS replaced L.L. Bean as the official outfitter of the Observatory.
