The Blue Hill Meteorological Observatory in
Milton, Massachusetts
Milton is a town in Norfolk County, Massachusetts, United States and an affluent suburb of Boston. The population was 28,630 at the 2020 census. Milton is the birthplace of former U.S. President George H. W. Bush, and architect Buckminster Fuller ...
is the foremost structure associated with the history of weather observations in the United States. Located atop
Great Blue Hill
Great Blue Hill is a hill of 635 feet (194 m) located within the Blue Hills Reservation in Milton, Randolph and Canton, Massachusetts, about south of downtown Boston. It is the highest point in Norfolk County and the Greater Boston area.
The ...
about 10 miles south of
Boston
Boston (), officially the City of Boston, is the capital city, state capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts, as well as the cultural and financ ...
,
, it is home to the oldest continuous weather record in
North America, and was the location of the earliest kite soundings of the atmosphere in North America in the 1890s, as well as the development of the
radiosonde
A radiosonde is a battery-powered telemetry instrument carried into the atmosphere usually by a weather balloon that measures various atmospheric parameters and transmits them by radio to a ground receiver. Modern radiosondes measure or calcula ...
in the 1930s.
Founded by
Abbott Lawrence Rotch in 1884, the observatory took a leading role in the newly emerging science of meteorology and was the scene of many of the first scientific measurements of upper atmosphere weather conditions, using kites to carry weather instruments aloft. Knowledge of wind velocities, air temperature and relative humidity at various levels came into use as vital elements in weather prediction due to techniques developed at this site. By 1895 the observatory was the source of weather forecasts of remarkable accuracy. On August 4, 1894 the first atmospheric sounding in the world was accomplished at the observatory, with a weather kite carrying a thermograph 2,030 feet above sea level. On October 8, 1896, a record of 8740 feet (2,665 m) was achieved for a weather kite. During the
Great New England Hurricane of 1938
The 1938 New England Hurricane (also referred to as the Great New England Hurricane and the Long Island Express Hurricane) was one of the deadliest and most destructive tropical cyclones to strike Long Island, New York, and New England. The storm ...
, the observatory measured the strongest wind gust ever directly measured and recorded in a hurricane at 186 mph (299 km/h).
The observatory remains active to this day, continuing to add to its database of weather observations now more than one hundred years old, and stands as a monument to the science of meteorology in the United States.
History
Site
The Blue Hill Meteorological Observatory was founded by American
meteorologist
A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while th ...
Abbott Lawrence Rotch in 1885. By the time he graduated from the
Massachusetts Institute of Technology
The Massachusetts Institute of Technology (MIT) is a Private university, private Land-grant university, land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern t ...
in 1884, Rotch had conceived and carried into execution his plans for the erection of a meteorological observatory on the summit of Great Blue Hill, ten miles south of
Boston, Massachusetts in the
Blue Hills Reservation
Blue Hills Reservation is a state park in Norfolk County, Massachusetts in the United States. Managed by the Massachusetts Department of Conservation and Recreation, it covers parts of Milton, Quincy, Braintree, Canton, Randolph, and Dedham. ...
, a 6,000-acre (24 km²) public park managed by the
Massachusetts Department of Conservation and Recreation
The Department of Conservation and Recreation (DCR) is a state agency of the Commonwealth of Massachusetts, situated in the Executive Office of Energy and Environmental Affairs. It is best known for its parks and parkways. The DCR's mission ...
. Rotch chose the site because the elevation of 635 feet was the highest point within ten miles of the Atlantic Ocean, on the East Coast south of central Maine. The Observatory was founded as a weather station and research facility. This location afforded early weather scientists a unique opportunity for recording extremes of weather and experimenting with weather-recording instruments.
The observatory building was completed by the end of 1884 and the first regular observations were begun on February 1, 1885. Rotch became the first director of the observatory and maintained it at his own expense until his death in 1912 when he bequeathed it to
Harvard University
Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...
with an endowment of $50,000, which grew to $111,000 in the twelve years after his death.
The building

Construction of the observatory was started by Rotch in 1884 using his own private funds, and designed by architects
Rotch & Tilden. The original structure consisted of a two-story circular tower and an adjoining housing unit which contained two bedrooms, a dining room and a kitchen. In 1889, a two-story east wing was added to provide additional working space for research, domestic chores, and the library.
In 1902, a two-story west wing containing a new library was added to provide additional work space. A steel fire door and brick wall connect the library to the earlier masonry structure. A timbrel vault (18 by 35 ft) of cohesive tiles spans the library. The timbrel vault tile roof is believed to have been installed by the Guastavino Company using an extremely tenacious mortar developed by
Rafael Guastavino, the founder of the firm.
Native stone, gathered from the summit of the Great Blue Hill, was used for the two-story tower, adjoining housing unit, and the east and west wings.
Copper sheathing
Copper sheathing is the practice of protecting the under-water hull of a ship or boat from the corrosive effects of salt water and biofouling through the use of copper plates affixed to the outside of the hull. It was pioneered and developed by ...
was used for roofing. A stone wall and iron fence were erected in 1905 to provide security for the building and instruments and privacy for the staff. The original stone tower eventually proved to be unsuitable. Wind-driven rain penetrated its walls, damaging the instruments and records. Vibration from the instruments on masts atop the tower contributed to the structural problems.
In 1908, the original tower was demolished and a new reinforced three-story late
Gothic Revival concrete tower, 20 feet 6 inches wide and 32 feet 8 inches high was constructed in its place. The concrete construction of the tower was chosen specifically to provide the maximum amount of stability and durability in the event of high winds. The tower has a crenelated top and a cornice containing
dentils
A dentil (from Lat. ''dens'', a tooth) is a small block used as a repeating ornament in the bedmould of a cornice. Dentils are found in ancient Greek and Roman architecture, and also in later styles such as Neoclassical, Federal, Georgian Rev ...
. The windows are double-hung sash with a shallow recessed arch over the windows on the first and second floors.

The new tower provided the durable weather-resistant, vibration-free environment necessary for accurate instrument readings. The first floor of the tower contains the director's office. The weather bureau is on the second floor and a laboratory and access to the roof are found on the third floor. Various wind gauges and other meteorological recording instruments are attached to the roof of the tower. The observatory still retains barometers and other instrumentation dating from the late 19th century. These instruments are used to calibrate the modern instrumentation to preserve the accuracy and integrity of the data base dating back to 1885.
In 1962, a metal tower containing a
siderostat for collecting the sun's rays and directing them by mirrors to an optical bench inside the observatory, was erected adjacent to the west wing for studies related to the upper atmosphere. This project was abandoned after a few years. This tower, with its mirrors still present, is no longer in use.
In 1980, the building was listed in the
National Register of Historic Places
The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artist ...
as "Great Blue Hill Weather Observatory", as part of a multiple property nomination by the Commonwealth of Massachusetts entitled "Prehistoric and Historic Resources of the Blue Hills and Neponset River Reservations and Selected Adjacent Lands".
In 1981, the Metropolitan District Commission transferred responsibility for the observatory to the Blue Hill Weather Club, a local group of supporters, who plan to restore the observatory and establish a weather museum on the site. The observatory will be kept open to continue its record of continuous weather observations. The
National Weather Service
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
continues to operate an
Automated Surface Observing System at the site.
A white marble stone containing a summary record of climatological data from 1885 to 1984 and dedicated to the memory of Abbott Lawrence Rotch is located on the front yard of the building.
It was declared a
National Historic Landmark
A National Historic Landmark (NHL) is a building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance. Only some 2,500 (~3%) of over 90,000 places listed ...
in 1989 with name "Blue Hill Meteorological Observatory".
In 2021, a major $2 million renovation of the observatory began. The renovation is expected to be completed by April 2023. Many parts of the building are being upgraded, and the renovations include a new concrete wall, new ceilings, new windows, and increased weatherproofing.
During the renovation the observatory is closed to the public, however the gift shop is still functional as it has moved outdoors. The renovation has not interfered with daily weather observations taken at the observatory. When the renovation is complete, there will be new exhibits and programs.
History of its operations

Under Rotch's leadership, the Blue Hill Meteorological Observatory quickly became famous for its pioneering studies of the upper atmosphere. The study of cloud heights, directions and velocities that Rotch carried out at the Blue Hill Observatory made significant contributions to the knowledge of clouds in the early years of the 20th century.
Rotch continued to work at the Blue Hill Observatory until his death on April 7, 1912. Under the terms of his will, the observatory was given to Harvard University with an endowment of $50,000 for operating costs. Harvard operated the observatory until 1971 when it disassociated itself from the site. The Rotch endowment was kept by Harvard.
After 1912, the Blue Hill Meteorological Observatory continued to operate as an active meteorological observatory. Weather observations and recordings have continued to this day, providing modern meteorologists with a record of uninterrupted climatological observations that is unique in the world.
Since these recordings were obtained from the same site with virtually no environmental change, they provide an important index to
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
. This information is of special importance to students of climatic change, in an age where so many weather records are flawed by environmental and procedural changes, and by repeated moves of the observing site over a number of years. For this reason, the
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...
designated the Blue Hill Observatory one of 26 International Benchmark stations within the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
.
During the 1950s, the site housed a research group that used
radar
Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
to scan approaching thunder storms as far away as western New York State, as part of an inquiry into the causes of lightning. Findings by this group were instrumental in the development of the US
weather radar
Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...
program. The installation consisted of a steel tower supporting a second-hand military radar set, several
Quonset hut
A Quonset hut is a lightweight prefabricated structure of corrugated galvanized steel having a semi cylindrical cross-section. The design was developed in the United States, based on the Nissen hut introduced by the British during World War ...
s and box trailers, surrounded by a chain-link fence. Group members were on call to monitor the radar whenever severe storms could be observed. Data were also collected from a network of amateur co-operative observers who corresponded by mail. This era coincided with the end of the long career of the famous Director of the Observatory, Dr. Charles Brooks, said to be one of the few who accurately forecast the path of the destructive
Hurricane of September, 1938.
Accomplishments
Since 1885, the staff of the observatory and others have documented the scientific work completed at the Blue Hill Observatory in almost 900 scientific publications. The Observatory's first century is a distinguished history of contribution to the development of meteorology. Measurements at the observatory have continued on a daily basis since the day it first opened in 1885, making the observatory one of the oldest continually active weather and climate monitoring stations in the United States.
[National Park Service]
Astronomy and Astrophysics: Blue Hill Meteorological Observatory.
Retrieved on 2006-12-03.
See also
*
List of astronomical observatories
This is a list of astronomical observatories ordered by name, along with initial dates of operation (where an accurate date is available) and location. The list also includes a final year of operation for many observatories that are no longer in ...
*
List of National Historic Landmarks in Massachusetts
The Commonwealth of Massachusetts has a total of 191 National Historic Landmarks (NHLs) within its borders. This is the second highest statewide total in the United States after New York, which has more than 250. Of the Massachusetts NHLs, 57 ...
*
National Register of Historic Places listings in Milton, Massachusetts
References
External links
Blue Hill Observatory & Science Center- official site
{{Authority control
Meteorological observatories
National Historic Landmarks in Massachusetts
Milton, Massachusetts
Infrastructure completed in 1885
Buildings and structures on the National Register of Historic Places in Massachusetts
National Register of Historic Places in Milton, Massachusetts
Science museums in Massachusetts
Museums in Norfolk County, Massachusetts
Atmospheric sounding