Blue Hill Meteorological Observatory Climate Data

Extensive work is in progress to transfer over 135 years of primary daily data observations including maximum and minimum temperature, precipitation, snowfall, snow cover, wind speed, sunshine and other parameters. This process will fill gaps and remove inconsistencies in the existing database and begin the process of digitizing data that has never been tabulated before. The objective is to generate the best possible collection of BHO daily climate data to support ongoing and future climate research projects. All data files require acceptance of the Observatory's Data Use & Privacy Policy prior to download. Expanded member files with longer historical records are also available below. As additional datasets are processed, they will be made available to Observatory members or researchers here or on request.

Agreement required — click any file below to review and accept the Data Use & Privacy Policy

Temperature

Hazen Temperature Shelter Hazen Temperature Shelter

The daily highest and lowest extreme temperatures are recorded at Blue Hill every day using two different thermometers in the white, shuttered Hazen temperature shelter within the instrument enclosure on the summit to the northeast of the Observatory. The maximum thermometer uses mercury in glass with a small constriction that allows the mercury to rise with the temperature, but prevents it from dropping until it is manually reset. The minimum thermometer contains an alcohol-based fluid that contains a floating index that drops with the temperature and marks the lowest temperature reached until the index is reset. The shelter also contains a psychrometer for measuring the current dry bulb and wet bulb temperatures that are used to derive the dew point and relative humidity. Hourly temperatures for every day are derived from a thermograph chart recorder also in the shelter using the manually observed temperatures as reference data points.

Samples of the daily temperature data for the years 2010–2021 are provided below in the form of Excel spreadsheets, which contain the recorded maximum and minimum temperatures for each day in each month of the year.

Precipitation

Rain Gauge Equipment Manual Weighing Rain Gauge, Snow Board, Ombroscope, and Standard 8-inch Rain Gauge (left to right)

Precipitation is recorded daily using a variety of equipment in the outdoor instrument enclosure near the Observatory. Manual readings of precipitation at three, six and 24-hour intervals are obtained by inserting a measuring stick into the standard 8-inch rain gauge, which is surrounded by metal slats to protect the falling precipitation from being blown away from the gauge by strong winds. Hourly precipitation is derived from the continuous chart recording of precipitation attached to the weighing rain gauge and by calibrating the amounts to those recorded in the standard gauge. The beginning and ending time of precipitation is recorded by an ombroscope, which consists of a chart-covered, clock-driven rotating cylinder inside the metal case that positions a small opening directly over the water-sensitive chart. Snowfall amounts are derived as an average measurement from several locations including on the white snow board (one of two in the enclosure).

Samples of the daily precipitation and snowfall data for the years 2010–2021 are provided below, containing the recorded liquid equivalent precipitation (including rain and melted snow and sleet) and the measured frozen precipitation for each day in each month of the year.

Bright Sunshine Duration

Campbell-Stokes Sunshine Recorder Campbell-Stokes Sunshine Recorder

A Campbell-Stokes sunshine recorder has been in use to measure bright sunshine duration at BHO since 1886, representing the longest such record of sunshine in North America. The parameter is referred to as bright sunshine since sunlight must be of sufficient intensity to scorch a paper card placed under the glass sphere to record the daily duration of sunshine. The recently tabulated daily sunshine data have been studied to assess the presence of climate change signals, and a paper based on this work has been published in the Bulletin of the American Meteorological Society.

A sample of the daily sunshine data for the years 2010–2021 is provided below, containing for each month of the year the recorded sunshine hours, minutes and percent of possible for each day.

Monthly Means and Extremes

Click here to see the complete list of monthly means for the 130-year period 1891–2020 and monthly extremes for the full period of record for temperature, precipitation, snowfall, and wind.

Climate Data Graphics

Click here to see plots of the Blue Hill climate data for the full period of record for temperature, precipitation, snowfall, wind speed, sunshine, and other parameters.

Blue Hill Observatory & Science Center · Legal

Data Use & Privacy Policy

Please read the full Policy before accessing Observatory data · Effective January 1, 2025

Notice: By accessing, downloading, or using any Blue Hill Observatory data or services, you unconditionally accept and agree to be bound by this Policy in its entirety. If you do not agree, you may not access or use Observatory data.
Effective January 1, 2025 · Milton, Massachusetts · bluehill.org
Part I — Data Use Policy
§ 01

Ownership and Proprietary Rights

All observational records, compiled datasets, metadata, database structures, and related materials provided by the Blue Hill Observatory & Science Center are the exclusive property of the Blue Hill Observatory & Science Center. The Observatory has maintained continuous weather observations at the summit of Great Blue Hill since 1885, and the entirety of that record — its compilation, structure, curation, and organization — constitutes a proprietary database protected under applicable United States law, including copyright law and common law database protections.

All rights not expressly granted in this Policy are reserved by the Observatory. No access to or use of Observatory data shall be construed as a waiver of any rights or as a license to use data beyond the scope expressly stated herein.

§ 02

Governing Law and Jurisdiction

This Policy shall be governed by and construed in accordance with the laws of the Commonwealth of Massachusetts, without regard to its conflict of law provisions. For interactions with international users, this Policy shall apply to the maximum extent permitted by applicable local law.

Any dispute arising from or related to this Policy shall be subject to the exclusive jurisdiction of the state and federal courts located in Norfolk County, Massachusetts. By accessing Observatory data, all users consent to personal jurisdiction in Massachusetts and waive any objection to the venue or inconvenience of such forum.

§ 03

Permitted Uses

Observatory data are made available for the following limited, non-commercial purposes only:

  • Personal study and analysis
  • Educational classroom use
  • Student projects
  • Non-commercial academic research
  • Publication of analyses, figures, models, or conclusions derived from the data, subject to the attribution requirements of Section 4

All other uses require prior written authorization from the Observatory.

§ 04

Attribution Requirement

Any use of Observatory data in any published, presented, or publicly distributed work must include the following verbatim acknowledgment:

"Data provided by the Blue Hill Observatory & Science Center, Milton, Massachusetts. Continuous weather observations since 1885."

Failure to include proper attribution is a material violation of this Policy.

§ 05

Prohibited Uses

Unless explicitly authorized in writing, Users may not:

  • Resell, license, sublicense, or commercially exploit Observatory data in any form
  • Redistribute the dataset in whole or in part to any third party
  • Publish the dataset for download by third parties
  • Host, mirror, or archive the dataset on any external website, repository, or storage service
  • Upload the dataset to any public or institutional data repository
  • Provide the data through APIs, automated services, or subscription platforms
  • Incorporate the data into any commercial product, software, application, or service
  • Use the data for AI or machine learning systems intended for commercial use or external distribution
  • Use the data to create derivative datasets that enable reconstruction of the underlying observations
§ 06

Commercial Licensing

Organizations seeking to use Observatory data for commercial purposes must obtain a license prior to any such use. Licensing inquiries: [email protected].

§ 07

Automated Access

Automated scraping, bulk harvesting, or systematic downloading of Observatory data is strictly prohibited without prior written authorization.

§ 08

Enforcement and Remedies

Violation of this Policy may result in immediate revocation of data access, pursuit of legal remedies available under United States law, and referral to applicable authorities. The Observatory reserves all rights to seek injunctive relief, damages, and attorneys' fees in connection with any unauthorized use of its data.

Part II — Privacy Policy
§ 09–10

Scope & Information Collected

This section governs the collection, use, storage, and disclosure of personal information from visitors to the Blue Hill Observatory website and users of its data services. The Observatory may collect contact information (name, email, organization) when voluntarily submitted, usage data including IP addresses and pages visited, and data download records.

§ 11–12

How We Use Information & Retention

Information is used solely for: responding to inquiries and licensing requests; monitoring and enforcing compliance with this Policy; improving website performance; and communicating Observatory news to opted-in users. The Observatory does not sell, rent, or share personal information with third parties for marketing purposes. Data access records may be retained indefinitely for compliance and enforcement purposes.

§ 13

International Users and Data Transfers

The Observatory is located in the United States. International users acknowledge their information will be processed in the United States under U.S. law. Users requiring specific data processing agreements under non-US law must contact [email protected] before accessing data.

§ 14–16

Cookies, Security & Children's Privacy

The Observatory website may use cookies for analytics and functionality. By continuing to use the site, users consent to cookie use. The Observatory implements reasonable measures to protect personal information but cannot guarantee absolute security. Observatory data services are not directed at children under 13.

Part III — General Provisions
§ 17–20

Modifications, Severability, Entire Agreement & Contact

The Observatory reserves the right to modify this Policy at any time. Updated versions will be posted at bluehill.org. Continued use of Observatory data following any modification constitutes acceptance of the revised Policy. This Policy constitutes the entire agreement between the User and the Observatory. Questions and licensing inquiries: Blue Hill Observatory & Science Center, Milton, Massachusetts — [email protected]

By accessing, downloading, or using any Blue Hill Observatory data or services, you acknowledge that you have read, understood, and agree to be bound by this Policy.
Effective January 1, 2025 · Blue Hill Observatory & Science Center · Milton, Massachusetts
↓ Scroll to read the full Policy — the agreement checkbox will unlock at the bottom