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Spring 2025 Summary – Tied for Fourth Warmest on Record

June 4, 2025

Blue Hill Observatory Spring (Mar-May) 2025 Summary:  Spring 2025 temperature and precipitation were well above average with much less snowfall and less…

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Blue Hill Observatory Spring (Mar-May) 2025 Summary: 

Spring 2025 temperature and precipitation were well above average with much less snowfall and less sunshine than expected. The approximated 24-hour mean temperature for spring of 49.0 deg F was 4.1 degrees warmer than the 1891-2020 130-year average for the season, and it was 2.6 degrees warmer than the 1991-2020 30-year average. Spring 2025 tied as the fourth warmest on record. The average maximum temperature of 59.0 deg F was 3.3 degrees warmer than the 30-year normal, which tied as the sixth warmest on record. The average minimum temperature of 39.8 deg F was 2.1 degrees warmer than the 30-year normal, which tied as the seventh warmest on record. The warmest temperature during spring was 84F on May 3rd, and the lowest temperature was 8F on March 3rd. The mean water vapor pressure, which is an absolute measure of water vapor in the air, was the second highest on record for spring at 8.8 mb, which corresponds to a mean dew point of about 41F. This amount was above the long-term mean water vapor pressure for spring of 7.4 mb, which equals a mean dew point of about 37F. The season was wetter than average, and the total precipitation was 16.09 inches, which was 1.99 inches more than the 30-year normal. The wettest month was May with 7.62 inches, which offset the slightly below average precipitation in March and April. The greatest amount in 24 hours was 3.73 inches of rain, which included a thunderstorm and gusty winds on May 22nd-23rd. There were six thunderstorm days during spring, including one in April and five in May. The total snowfall for the season was just 1.7 inches, all occurring in April, which was 16.1 inches below the seasonal average. The lowest sea-level pressure during spring was 29.04 inches on May 31st, which tied the lowest pressure ever observed in May, and the highest sea-level pressure was 30.56 inches on April 2nd. The mean wind speed was 12.9 mph, and the prevailing wind direction was from the south-southwest. The highest wind gust was 69 mph from the south during a warm rain storm on March 6th. Spring sunshine was below average with 561.7 hours of bright sunshine, or 47 percent of possible, which was three percent less than the long-term average for the season.

BHO Warmest Spring (Mar-May) Approximated 24-Hour Mean Temperature, deg F (1885-2025):

1) 51.3 in 2010
2) 50.9 in 2012
3) 49.4 in 1991
4) 49.0 in 1977
   49.0 in 2025
6) 48.4 in 1998
   48.4 in 2022
8) 48.3 in 2023
9) 48.2 in 1976
10) 48.1 in 1945

BHO Warmest Spring (Mar-May) Average Maximum Temperature, deg F (1885-2025):

1) 61.4 in 2010
2) 61.1 in 2012
3) 60.5 in 1991
4) 60.3 in 1977
5) 59.6 in 1945
6) 59.0 in 1976
   59.0 in 2022
   59.0 in 2025
9) 58.5 in 1903
   58.5 in 1921
   58.5 in 2021

BHO Warmest Spring (Mar-May) Average Minimum Temperature, deg F (1885-2025):

1) 9.1 in 2012
2) 42.4 in 2010
3) 40.5 in 1945
4) 40.4 in 1998
   40.4 in 2024
6) 39.9 in 1973
7) 39.8 in 1991
   39.8 in 2025
9) 39.7 in 1979
   39.7 in 2023

BHO Highest Spring (Mar-May) Average Water Vapor Pressure, mb (1932-2025):

1) 9.1 in 2012
2) 8.8 in 2025
3) 8.7 in 1979
   8.7 in 2024
5) 8.6 in 1973
   8.6 in 2011

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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