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May 2020 Summary – Drier and Sunnier Than Average

June 13, 2020

Blue Hill Observatory May 2020 Summary: May was unusually dry and sunny with variable temperatures. The 24-hour adjusted mean temperature for the…

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Blue Hill Observatory May 2020 Summary:

May was unusually dry and sunny with variable temperatures. The 24-hour adjusted mean temperature for the month of 56.1 deg F was 0.8 degrees warmer than the 120-year average for May, but it was 0.1 degrees colder than the 1981-2010 30-year average. The average maximum temperature of 67.2 deg F was about 1 degree warmer than the 30-year mean. The average minimum temperature of 45.8 deg F was 2 degrees colder than the 30-year mean. The highest temperature observed all month was 84F on the 27th, and the lowest temperature was 31F on the 10th. This was the latest freeze since 32F was recorded on May 10th, 1977. However, it was followed by another freezing temperature of 32F on the 13th, which surpassed the previous daily record minimum temperature of 35F set in 1914 and 2005. This reading was also the second latest freeze ever recorded at the Observatory behind only 30F observed on May 16th, 1936. May precipitation totaled 2.75 inches, which was about an inch less than the long-term 120-year average and nearly an inch and a half less than the 30-year mean. The greatest precipitation in 24 hours was 0.94 inches on the 1st. Snowfall in May totaled a trace, which was recorded on the morning of the 9th. The final 2019-2020 seasonal snowfall was 31.9 inches, which was the lowest for any season since 24.2 inches was measured in 2011-2012. There was one thunderstorm during May that occurred late in the day on the 15th. The mean wind speed for the month was 12.7 mph, and the prevailing wind direction was from the west. The monthly peak gust was 52 mph from the west on a cool, breezy day following some rain and a trace of snow. May was much sunnier than average with 270.8 hours of bright sunshine, or 62 percent of possible, which was ten percent more than the long-term average.

Spring (Mar-May) 2020 Summary:

Spring 2020 was generally warmer, wetter and sunnier than average. The 24-hour adjusted mean temperature for the Spring season of 46.5 deg F was 1.7 degrees warmer than the 120-year average, and it was 0.4 degrees warmer than the 1981-2010 30-year average. Cool temperatures during the second half of April extended into mid-May, with the second latest freeze on record being observed on May 13th. Precipitation during Spring totaled 15.13 inches, with about half of this amount occurring in April, and this total was nearly three inches more than the 120-year average and about an inch more than the 30-year normal. Spring snowfall of 7.1 inches was about eight inches less than average. Spring was slightly sunnier than average with 51 percent of the possible bright sunshine, which was one percent more than the long-term Spring average of 50 percent.

BHO Latest Freezing Temperature, deg F (1885-2020):

1) 30F on 16 May 1936
2) 32F on 13 May 2020
3) 29F on 12 May 1907
   30F on 12 May 1963
5) 28F on 11 May 1900
   31F on 11 May 1907
   31F on 11 May 1913
   30F on 11 May 1923
9) 29F on 10 May 1900
   31F on 10 May 1902
   31F on 10 May 1947
   32F on 10 May 1966
   32F on 10 May 1977
   31F on 10 May 2020

Mike Iacono
Chief Scientist
Blue Hill Observatory


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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: data@bluehill.org.

§ 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 data@bluehill.org 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 — data@bluehill.org

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
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