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Saturday, September 20, 2025

September 20, 2025

BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA SATURDAY, SEPTEMBER 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, SEPTEMBER 20, 2025 ALL TIMES ARE IN EASTERN STANDARD TIME (EST) SUNRISE: 0530E SUNSET:  1744E THE FEEL OF AUTUMN TODAY UNDER ABUNDANT SUNSHINE…. What a gorgeous day in progress today. Plenty of sunshine has been the theme with only a few low and high clouds around to add a little character to the sky. A rather significant air mass change occurred last evening as the warm and humid air finally got pushed out of the region. Today is much more pleasant for outdoor activities with cooler temperatures and drier air. Temperatures dropped into the 40s and low 50s overnight with the cooler readings occurring in lower lying areas. Here on the summit we got down to 51F early this morning. Readings have been slow to rise today thanks to some ongoing cold air advection, albeit on the weakening as the day progresses. We have only reached the mid 60s by early this afternoon. The dew point has been generally in the mid to upper 40s so far through early this afternoon. Winds were a bit stronger overnight thanks to the cold air advection, but has been gradually decreasing through the day- light hours today. A north wind in the wee hours has become easterly by late this morning and early afternoon. The average speed for the day is around 8mph, but as mentioned, the trend has been for a decrease in speed. The peak gust for the day is 18mph, which occurred just before 12:30am this morning. Visibility is excellent today with a view around 70 miles all day! The maximum temperature so far today is 67F degrees, which is 4 degrees below the normal high of 71F. The minimum temperature since midnight is 51F degrees, which is 3 degrees below the normal low of 54F. ————————————————————– Today’s Observations: 7 A.M. Weather: Clear, few cirrus distant WSW-NW Temperature: 56F; Dew Point: 46F; Relative Humidity: 68% Wind: NE @ 7 kts Sea-level pressure: 1025.4 mb; 30.28 in. Hg: rising, then more slowly Visibility: 70 miles 6-hr Max temp: 56F 6-hr Min temp: 51F 24-hr Precip: 0.00 inches BHO SA 1155 CLR 70 254/56/46/0407/028/ FEW CI DSNT WSW-NW/ 8/001 51019 10056 20051 10 A.M. Weather: Clear, few stratocumulus SW-NW-NE, few cirrus distant WSW-NW-NE Temperature: 62F; Dew Point: 44F; Relative Humidity: 52% Wind: ENE @ 7 kts Sea-level pressure: 1026.8 mb; 30.32 in. Hg: rising, then more slowly Visibility: 70 miles 3-hr Precip: 0.00 inches BHO SA 1455 CLR 70 268/62/44/0607/032/ FEW SC SW-NW-NE FEW CI DSNT WSW-NW-NE/ 8/501 51014 1 P.M. Weather: Clear, few cumulus distant ESE-SSE and distant W-N-NNE, few cirrus WSW-N-ENE Temperature: 66F Dew Point: 47F; Relative Humidity: 50% Wind: ESE @ 4 kts, wind light and variable Sea-level pressure: 1026.2 mb; 30.30 in. Hg: falling, then more rapidly Visibility: 70 miles 6-hr Max temp: 67F 6-hr Min temp: 56F 6-hr Precip: 0.00 inches BHO SA 1755 CLR 70 262/66/47/1204/030/ FEW CU DSNT ESE-SSE AND DSNT W-N-NNE FEW CI WSW-N-ENE WND L/V/ 8/201 58006 10067 20056 ————————————————————– SUMMARY FOR FRIDAY, SEPTEMBER 19, 2025 TEMPERATURE (DEGREES F) MAX…….80   NORMAL…..72 MIN…….57   NORMAL…..55 MEAN……69   NORMAL…..63 DEPARTURE FROM 30-YEAR (1991-2020) NORMAL…………….+6 TOTAL DEPARTURE FOR THE MONTH………………………-11 [-0.8 DEGREES/DAY] HEATING DEGREE DAYS (SEASON: JUL 2025 THRU JUN 2026) TOTAL HEATING UNITS FOR YESTERDAY……………..0  DEPARTURE……..-4 TOTAL HEATING UNITS FOR THE MONTH…………….26  DEPARTURE…….-13 TOTAL HEATING UNITS FOR THE SEASON……………46  DEPARTURE…….-11 TOTAL HEATING UNITS LAST SEASON TO DATE……….21  DEPARTURE…….+25 COOLING DEGREE DAYS (SEASON JAN 2025 THRU DEC 2025) TOTAL COOLING UNITS FOR YESTERDAY……………..4  DEPARTURE……..+2 TOTAL COOLING UNITS FOR THE MONTH…………….38  DEPARTURE…….-23 TOTAL COOLING UNITS FOR THE SEASON…………..710  DEPARTURE…….+53 TOTAL COOLING UNITS LAST SEASON TO DATE………753  DEPARTURE…….-43 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 F420C (Official)………..24 N    @   10:36 P.M. VECTOR #1 (1-Sec)……….24 N    @   10:36 P.M. VECTOR #2 (1-Sec)……….24 N    @   10:36 P.M. DAVIS #1……………….22 NNE  @   10:37 P.M. DAVIS #2 ………………22 NE   @   10:37 P.M. RMY #1 (Instantaneous)…..23 N    @   10:36 P.M. RMY #2 (Instantaneous)…..24 N    @   10:36 P.M. MERLIN…………………22 NNW RICHARDS (C5C) (Inst)……22 N    @   08:34 P.M. FASTEST MILE: CONTACTING ANEMOMETER/OFFICIAL………………15 WNW  @   02:22 P.M. MAXIMUM 2-MINUTE VECTOR #1 AVERAGE…………..15 N    @   10:50 P.M. MAXIMUM 2-MINUTE VECTOR #2 AVERAGE…………..16 WNW  @   01:39 A.M. MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………15 W    @   02:22 P.M. MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………15 NW   @   01:39 A.M. MAXIMUM 2-MINUTE RMY #1 AVERAGE……………..15 N    @   10:50 P.M. MAXIMUM 2-MINUTE RMY #2 AVERAGE……………..16 WNW  @   01:39 A.M. MAXIMUM 2-MINUTE RICHARDS (C5C) AVERAGE………15 NW   @   03:12 P.M. AVERAGE WIND SPEED AND DIRECTION: CONTACTING/OFFICIAL……..10.3 NW [248 total miles] VECTOR #1………………10.5 VECTOR #2………………11.1 DAVIS #1……………….10.7 NW DAVIS #2……………….10.8 NNW RMY #1…………………10.2 NW RMY #2…………………10.9 NW RICHARDS (C5C)………….10.7 PRECIPITATION (INCHES) THROUGH THIS MORNING (EST): TOTAL PRECIPITATION 24 HRS ENDING 7 A.M……..0.00 DEPARTURE…..-0.15 TOTAL PRECIPITATION FOR THE MONTH…………..2.58 DEPARTURE…..+0.17 TOTAL PRECIPITATION FOR THE YEAR (2025)…….33.91 DEPARTURE…..-3.11 ————————————————————– PRELIMINARY CLIMATE SUMMARY FOR SEPTEMBER CALENDAR DAY DATA DATE: MAX/MIN/MEAN/DEP/PRECIP/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 9/1   73/55/64/-5/0.00/221/28            23 NE  VEC1 23 ENE RMY 23 9/2   77/58/68/-1/0.00/714/91            18 ESE VEC1 19 ESE RMY 18 9/3   78/57/68/0/0.00/719/92             21 SSW VEC1 21 SSW RMY 21 9/4   81/56/69/+1/0.00/694/89            26 SSW VEC1 27 SSW RMY 28 9/5   82/63/73/+5/0.12/404/52            30 SSW VEC1 31 SSW RMY 33 9/6   84/64/74/+6/1.05/457/59            55 W   VEC1 55 W   RMY 57 TSTM 9/7   64/56/60/-7/0.97/000/00            16 WNW VEC1 16 NNE RMY 15 9/8   68/49/59/-8/0.00/508/66            21 NW  VEC1 21 NW  RMY 24 9/9   70/53/62/-5/0.00/697/91            22 ENE VEC1 23 E   RMY 23 9/10  65/54/60/-6/0.00/183/24            24 NE  VEC1 25 NE  RMY 25 9/11  77/51/64/-2/0.00/714/94            21 N   VEC1 17 N   RMY 18 9/12  71/56/64/-2/0.00/735/97            24 ENE VEC1 24 NNE RMY 23 9/13  76/55/66/+1/T/634/84               26 S   VEC1 26 S   RMY 25 9/14  79/57/68/+3/0.00/572/76            15 NE  VEC1 15 SW  RMY 15 9/15  72/57/65/0/0.00/689/92             20 N   VEC1 19 N   RMY 18 9/16  71/55/63/-1/0.00/403/54            20 E   VEC1 19 ESE RMY 19 9/17  71/55/63/-1/T/424/57               22 E   VEC1 22 E   RMY 21 9/18  75/61/68/+5/0.44/252/34            20 S   VEC1 20 S   RMY 20 TSTM 9/19  80/57/69/+6/0.00/715/97            24 N   VEC1 24 N   RMY 23 9/20 The low since midnight is 51F, the daily normal low is 54F. ————————————————————– SEPTEMBER DAILY RECORDS TO DATE NONE. ————————————————————– DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated) RECORDS FOR SEPTEMBER 20 HIGH 90 IN 1983 LOW 34 IN 1979 PRECIP 4.57 INS IN 1899 PEAK GUST 44 MPH NE IN 1972 RECORDS FOR SEPTEMBER 21 HIGH 91 IN 1895 LOW 35 IN 1929, 1956, 1962 PRECIP 5.58 INS IN 1961 (HURRICANE ESTHER; RETURNED AS TS SEPT 25-26TH) PEAK GUST 186 MPH S IN 1938 (GREAT NEW ENGLAND HURRICANE; CALCULATED GUST, STATION RECORD) TODAY’S REPORT PREPARED BY: Matt Douglas
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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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