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Summer 2026 Summary – Tied for Warmest and Fourth Sunniest on Record

September 4, 2026

Blue Hill Observatory Summer (Jun-Aug) 2026 Summary:  Summer 2026 was exceptionally warm, and it was drier and much sunnier than expected. The…

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Blue Hill Observatory Summer (Jun-Aug) 2026 Summary: 

Summer 2026 was exceptionally warm, and it was drier and much sunnier than expected. The approximated 24-hour mean temperature for summer of 71.6 deg F was 4.1 degrees warmer than the 1891-2020 130-year average for the season, and it was 2.4 degrees warmer than the 1991-2020 30-year average. Summer 2026 tied with Summer 2016 as the warmest on record. The average maximum temperature of 81.9 deg F was 2.8 degrees warmer than the 30-year normal, and it was the fifth warmest on record. The average minimum temperature of 62.1 deg F was 0.8 degrees warmer than the 30-year normal, and it was the eighth warmest on record. There were two heat waves during Summer 2026, on July 1st-4th and on August 6th-8th, and it was the fifth of the last seven summers to have two heat waves. There were 10 ninety-degree days, which was four more than average. Summer 2026 was generally warm all season; June was the second warmest and August tied as the sixth warmest on record. The warmest temperature was 99F on July 2nd, and the lowest temperature was 45F on June 1st and 2nd. The average water vapor pressure was 18.7 mb, which corresponded to a mean dew point of 62F. This value was higher than the long-term average vapor pressure for summer of 17.6 mb, which corresponds to an average dew point of 60F. The season was drier than average, and the total precipitation was 9.19 inches, which was 2.82 inches less than the 30-year normal. More than half of the summer rainfall fell during the wettest month, July, while June and August were much drier than average. Nearly one-fourth of the season’s rain, 2.17 inches, fell during a single rainstorm on July 6th-8th, which also interrupted the very warm start to July. The greatest rainfall amount in 24 hours during summer was 2.11 inches on July 7th. There were nine thunderstorm days during summer, which was five fewer than average for the season. The highest sea-level pressure was 30.29 inches on June 8th, and the lowest sea-level pressure was 29.47 inches on June 18th from a storm passing inland over southern Canada. The mean wind speed was 10.2 mph, which tied for the seventh lowest on record, and the prevailing wind direction was from the west-northwest. The highest wind gust was 51 mph from the south on June 18th. Summer sunshine was well above average with 868.6 total hours of bright sunshine, or 67 percent of possible, which was ten percent more than the long-term average for the season, and Summer 2026 was the fourth sunniest on record.

BHO Warmest Summer (Jun-Aug) Approx. 24-Hour Mean Temperature, deg F (1885-2026):

1) 71.6 in 2016
   71.6 in 2026
3) 71.5 in 2022
4) 71.3 in 2010
5) 71.1 in 2020
6) 70.9 in 2018
7) 70.8 in 1949
8) 70.7 in 2024

BHO Warmest Summer (Jun-Aug) Average Maximum Temperature, deg F (1885-2026):

1) 83.0 in 1949
2) 82.9 in 2022
3) 82.4 in 2016
4) 82.1 in 2010
5) 81.9 in 2026
6) 81.5 in 1952
7) 81.3 in 2020
8) 81.0 in 2024

BHO Warmest Summer (Jun-Aug) Average Minimum Temperature, deg F (1885-2026):

1) 63.1 in 2020
2) 62.6 in 2022
3) 62.5 in 2010
4) 62.4 in 2018
   62.4 in 2021
6) 62.3 in 2016
   62.3 in 2024
8) 62.1 in 1973
   62.1 in 1999
   62.1 in 2026

BHO Highest Summer (Jun-Aug) Bright Sunshine, hours (1886-2026):

1) 919.7 in 1971 [71%]   
2) 888.0 in 2016 [68%]   
3) 876.0 in 1965 [68%]   
4) 868.6 in 2026 [67%]   
5) 864.1 in 2022 [67%]   
6) 863.8 in 1966 [67%]   
7) 862.5 in 2014 [66%]   
8) 861.7 in 1909 [66%]   

BHO Lowest Summer (Jun-Aug) Mean Wind Speed, mph (1885-2026):

1) 9.5 in 2023
2) 9.8 in 2025
3) 10.0 in 2019
   10.0 in 2021
   10.0 in 2024
6) 10.1 in 2020
7) 10.2 in 2012
   10.2 in 2026
9) 10.3 in 2008
   10.3 in 2009

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
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  • 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
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  • Publish the dataset for download by third parties
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§ 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

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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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