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Saturday, December 20, 2025

December 20, 2025

BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA SATURDAY, DECEMBER 20, 2025 ALL TIMES ARE…

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BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA SATURDAY, DECEMBER 20, 2025 ALL TIMES ARE IN EASTERN STANDARD TIME (EST) SUNRISE: 0710E SUNSET:  1614E COLD AIR RETURNS, PLENTY OF SUNSHINE…. Following the passage of a cold front and departure of yesterday’s storm system, skies cleared for the morning aside from a few distant stratocumulus. Some thin upper level clouds moved in from the southwest for the early afternoon, filtering the sunshine somewhat. The brief warm up we experienced yesterday due to strong southerly flow has quickly come to an end, with a cold, dry air mass moving back into place. The low this morning was in the upper 20s, with a high so far in the mid 30s. The dew point has remained in the upper teens. Winds were steady through the early morning hours, before dropping off quite dramatically right around sunrise. The average speed for the day so far is 15mph, primarily out of the west-northwest. The peak gust is approximately 46mph, occurring shortly after 2am this morning. Visibility is excellent today, with views reaching up to 70 miles by the late morning hours. The maximum temperature so far today is 36F degrees, which is 3 degrees below the normal high of 39F. The minimum temperature since midnight is 27F degrees, which is 3 degrees above the normal low of 24F. ————————————————————– Today’s Observations: 7 A.M. Weather: Clear, few stratocumulus distant NE-SW Temperature: 27F; Dew Point: 18F; Relative Humidity: 67% Wind: WNW @ 13G21 kts, peak wind WNW 32mph at 05:59 A.M. Sea-level pressure: 1016.0 mb; 30.00 in. Hg: rising, then more rapidly Visibility: 50 miles 6-hr Max temp: 32F 6-hr Min temp: 27F 24-hr Precip: 0.58 inches 24-hr Snowfall: 0.0 inches Snow Depth: 0 inches BHO SA 1155 CLR 50 160/27/18/3013G21/000/ FEW SC DSNT NE-SW PRESRR PK WND 2928/1059/ 8/500 53059 70058 10032 20027 10 A.M. Weather: Clear, few altocumulus distant S-WSW Temperature: 32F; Dew Point: 20F; Relative Humidity: 60% Wind: WNW @ 8 kts Sea-level pressure: 1019.5 mb; 30.11 in. Hg: rising unsteadily Visibility: 70 miles 3-hr Precip: 0.00 inches 3-hr Snowfall: 0.0 inches BHO SA 1455 CLR 70 195/32/20/3008/011/ FEW AC DSNT S-WSW/ 8/050 52035 1 P.M. Weather: Thin scattered cirrus, few altocumulus distant SW-N, few cirrostratus all quadrants Temperature: 36F; Dew Point: 18F; Relative Humidity: 47% Wind: W @ 7 kts Sea-level pressure: 1019.3 mb; 30.10 in. Hg: rising, then falling Visibility: 70 miles 6-hr Max temp: 36F 6-hr Min temp: 27F 6-hr Precip: 0.00 inches 6-hr Snowfall: 0.0 inches Snow Depth: 0 inches BHO SA 1755 250 -SCT 70 193/36/18/2707/010/ FEW AC DSNT SW-N FEW CS ALQDS/ 8/055 58002 10036 20027 ————————————————————– SUMMARY FOR FRIDAY, DECEMBER 19, 2025 TEMPERATURE (DEGREES F) MAX…….58   NORMAL…..39 MIN…….32   NORMAL…..24 MEAN……45   NORMAL…..32 DEPARTURE FROM 30-YEAR (1991-2020) NORMAL……………+13 TOTAL DEPARTURE FOR THE MONTH………………………-92 [-5.0 DEGREES/DAY] HEATING DEGREE DAYS (SEASON: JUL 2025 THRU JUN 2026) TOTAL HEATING UNITS FOR YESTERDAY…………….20  DEPARTURE…….-13 TOTAL HEATING UNITS FOR THE MONTH……………677  DEPARTURE…….+91 TOTAL HEATING UNITS FOR THE SEASON………….1794  DEPARTURE……..+4 TOTAL HEATING UNITS LAST SEASON TO DATE……..1521  DEPARTURE……+273 PEAK WIND GUST (MPH): Note: Instruments designated #1 = Main Tower, #2 = South Tower, F420C, Contacting, Merlin, and Richards are all on Main Tower. E=Estimated *=Last of multiple occurrences F420C (Official)………..79 S    @   11:48 A.M. VECTOR #1 (1-Sec)……….79 S    @   11:48 A.M. VECTOR #2 (1-Sec)……….79 SSE  @   11:48 A.M. DAVIS #1……………….81 S    @   12:46 P.M. DAVIS #2 ………………95 S    @   11:02 A.M. RMY #1 (Instantaneous)…..81 S    @   11:48 A.M. RMY #2 (Instantaneous)…..86 SSE  @   11:48 A.M. MERLIN…………………73 S RICHARDS (C5C) (Inst)……79 S    @   11:48 A.M. FASTEST MILE: CONTACTING ANEMOMETER/OFFICIAL………………54 SSE  @   11:49 A.M. MAXIMUM 2-MINUTE VECTOR #1 AVERAGE…………..53 SSE  @   11:49 A.M. MAXIMUM 2-MINUTE VECTOR #2 AVERAGE…………..55 SSE  @   11:26 A.M. MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………49 SSE  @   11:50 A.M. MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………62 S    @   12:14 P.M. MAXIMUM 2-MINUTE RMY #1 AVERAGE……………..51 SSE  @   11:49 A.M. MAXIMUM 2-MINUTE RMY #2 AVERAGE……………..52 SSE  @   11:26 A.M. MAXIMUM 2-MINUTE RICHARDS (C5C) AVERAGE………52 S    @   11:50 A.M. AVERAGE WIND SPEED AND DIRECTION: CONTACTING/OFFICIAL……..24.1 S [578 total miles] VECTOR #1………………23.1 VECTOR #2………………24.7 DAVIS #1……………….22.6 SSW DAVIS #2……………….25.3 SSW RMY #1…………………22.1 SSW RMY #2…………………24.0 SSW RICHARDS (C5C)………….22.3 PRECIPITATION (INCHES) THROUGH THIS MORNING (EST): TOTAL PRECIPITATION 24 HRS ENDING 7 A.M……..0.58 DEPARTURE…..+0.40 TOTAL PRECIPITATION FOR THE MONTH…………..1.68 DEPARTURE…..-1.71 TOTAL PRECIPITATION FOR THE YEAR (2025)…….46.14 DEPARTURE…..-5.72 SNOWFALL (INCHES) THROUGH THIS MORNING (EST): TOTAL SNOWFALL 24 HRS ENDING 7 A.M…………..0.0 DEPARTURE…..-0.5 TOTAL SNOWFALL FOR THE MONTH………………..2.4 DEPARTURE…..-4.2 TOTAL SNOWFALL FOR THE SEASON (2025-2026)…….2.5 DEPARTURE…..-6.6 ————————————————————– PRELIMINARY CLIMATE SUMMARY FOR DECEMBER CALENDAR DAY DATA DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN)/SUN(%)/PEAK GUST/VEC1/RMY GUST PEAK GUST: F420C (Official) VEC1: Vector #1 1-second gust RMY:  R.M. Young #1 wind gust recording system (Instantaneous) TSTM: Thunderstorm day (thunder heard some time during day) ….: Data not yet available, records not finalized M:    Missing data 12/1   42/27/35/-2/T/0.0/547/98          37 WNW VEC1 37 WNW RMY 38 12/2   36/27/32/-5/0.85/T/000/00         38 N   VEC1 38 NNE RMY 38 12/3   37/27/32/-4/0.06/0.6/423/76       28 NW  VEC1 29 NNW RMY 30 12/4   38/15/27/-9/T/T/255/46            60 NW  VEC1 59 WNW RMY 61 12/5   25/8/17/-19/T/T/510/92            30 NW  VEC1 30 NW  RMY 30 12/6   39/25/32/-3/T/T/122/22            21 W   VEC1 21 W   RMY 22 12/7   39/27/33/-2/0.00/0.0/248/45       24 W   VEC1 24 W   RMY 24 12/8   31/12/22/-13/T/T/457/83           43 NW  VEC1 43 NW  RMY 44 12/9   28/9/19/-15/0.00/0.0/452/82       33 SSW VEC1 33 SSW RMY 33 12/10  46/28/37/+3/0.04/T/187/34         50 SSW VEC1 50 SSW RMY 51 12/11  37/21/29/-5/0.00/0.0/450/82       51 WNW VEC1 51 WNW RMY 53 12/12  33/18/26/-8/0.00/0.0/532/97       41 W   VEC1 41 W   RMY 42 12/13  34/23/29/-4/0.00/0.0/038/07       28 SW  VEC1 28 SW  RMY 31 12/14  31/15/23/-10/0.13/1.8/000/00      39 NNW VEC1 39 NNW RMY 40 12/15  23/10/17/-16/0.00/0.0/496/91      40 NW  VEC1 40 NW  RMY 42 12/16  36/19/28/-4/0.00/0.0/437/80       29 SW  VEC1 29 SW  RMY 30 12/17  45/25/35/+3/0.00/0.0/196/36       43 SW  VEC1 42 SW  RMY 43 12/18  47/32/40/+8/0.00/0.0/…/..       32 S   VEC1 32 S   RMY 34 12/19  58/32/45/+13/0.60/0.0/…/..      79 S   VEC1 79 S   RMY 81 12/20  The low since midnight is 27F, the daily normal low is 24F. ————————————————————– DECEMBER DAILY RECORDS TO DATE 12/19 PEAK GUST OF 79 MPH S, BEAT THE OLD RECORD OF 68 MPH NE IN 1986. ————————————————————– DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated) RECORDS FOR DECEMBER 20 HIGH 61 IN 1957 LOW -16 IN 1942 PRECIP 1.69 INS. IN 1936 SNOWFALL 13.7 INS. IN 2009 PEAK GUST 75 MPH S IN 2002 RECORDS FOR DECEMBER 21 HIGH 62 IN 2018 LOW -10 IN 1942 PRECIP 2.37 INS. IN 1946 SNOWFALL 11.4 INS. IN 1954 PEAK GUST 77 MPH SSE IN 1957 TODAY’S REPORT PREPARED BY: Joshua Polen
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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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