Saturday, 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 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.

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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

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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

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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.

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SEPTEMBER DAILY RECORDS TO DATE

NONE.

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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