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Monday, April 21, 2025

April 21, 2025

BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA MONDAY, APRIL 21, 2025 ALL TIMES ARE…

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BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA

MONDAY, APRIL 21, 2025
ALL TIMES ARE IN EASTERN STANDARD TIME (EST)
SUNRISE: 0453E
SUNSET:  1833E

GREAT WEATHER CONDITIONS FOR MARATHON MONDAY….

For those running or watching the Boston Marathon, the
weather today did not disappoint. Seasonable temperatures,
filtered sunshine, and light winds combined to create great
racing/spectating conditions.

Sunshine remains filtered as we head into the afternoon, due to
persistent cirrus clouds ahead of a frontal boundary. Some mid-level
clouds are also moving in from the southwest, and have increased in
coverage in recent hours.

Temperatures are seasonable, with a low in the upper 30s and a
high so far in the low 60s. The air remains dry, with dew points
remaining in the 20s for much of the day.

Winds are light, with an average speed so far of only 7mph. Flow began
this morning out of the north-northwest, with direction becoming
quite variable thereafter. The peak gust is a measly 19mph occurring
around 1:15am.

Visibility is excellent with the dry air in place, with views
extending 60-70 miles.

The maximum temperature for today is 63F degrees, which is 4
degrees above the normal high of 59F. The minimum temperature
since midnight is 37F degrees, which is 3 degrees below the
normal low of 40F.

————————————————————–

Today’s Observations:

7 A.M.
Weather: Thin broken cirrus
Temperature: 45F; Dew Point: 25F; Relative Humidity: 45%
Wind: NNE @ 3 kts, wind light
Sea-level pressure: 1028.3 mb; 30.37 in. Hg: rising, then more slowly
Visibility: 70 miles
6-hr Max temp: 45F
6-hr Min temp: 37F
24-hr Precip:  0.00 inches
24-hr Snowfall: 0.0 inches
Snow Depth: 0 inches
BHO SA 1155 E250 -BKN 70 283/45/25/0203/037/ WND LGT/ 8/001 51007 10045 20037

10 A.M.
Weather: Thin broken cirrus, few altocumulus distant SW-W
Temperature: 54F; Dew Point: 24F; Relative Humidity: 31%
Wind: SSE @ 2 kts, wind light
Sea-level pressure: 1027.6 mb; 30.35 in. Hg: falling, then rising
Visibility: 70 miles
3-hr Precip:  0.00 inches
3-hr Snowfall: 0.0 inches
BHO SA 1455 E250 -BKN 70 276/54/24/1502/035/ FEW AC DSNT SW-W WND LGT/
8/051 55007

1 P.M.
Weather: Scattered cirrus, few altocumulus distant S-NW,
smoke plume distant SSW
Temperature: 62F Dew Point: 29F; Relative Humidity: 28%
Wind: SSW @ 5 kts, wind light
Sea-level pressure: 1024.1 mb; 30.24 in. Hg: falling, then more rapidly
Visibility: 60 miles
6-hr Max temp: 63F
6-hr Min temp: 45F
6-hr Precip:  0.00 inches
6-hr Snowfall: 0.0 inches
Snow Depth: 0 inches
BHO SA 1755 250 SCT 60 241/62/29/2005/024/ FEW AC DSNT S-NW K PLUME DSNT SSW
WND LGT/ 8/051 58035 10063 20045

————————————————————–

SUMMARY FOR SUNDAY, APRIL 20, 2025

TEMPERATURE (DEGREES F)
MAX…….67   NORMAL…..59
MIN…….45   NORMAL…..40
MEAN……56   NORMAL…..49

DEPARTURE FROM 30-YEAR (1991-2020) NORMAL……………+7
TOTAL DEPARTURE FOR THE MONTH……………………….0 [-0.2 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON: JUL 2024 THRU JUN 2025)
TOTAL HEATING UNITS FOR YESTERDAY……………..9  DEPARTURE……..-7
TOTAL HEATING UNITS FOR THE MONTH……………401  DEPARTURE………0
TOTAL HEATING UNITS FOR THE SEASON………….5330  DEPARTURE……-418
TOTAL HEATING UNITS LAST SEASON TO DATE……..4999  DEPARTURE……+331

COOLING DEGREE DAYS (SEASON JAN 2025 THRU DEC 2025)
TOTAL COOLING UNITS FOR YESTERDAY……………..0  DEPARTURE………0
TOTAL COOLING UNITS FOR THE MONTH……………..2  DEPARTURE……..+1
TOTAL COOLING UNITS FOR THE SEASON…………….2  DEPARTURE……..+1
TOTAL COOLING UNITS LAST SEASON TO DATE………..0  DEPARTURE……..+2

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)………..53 NW   @   08:36 A.M.
VECTOR #1 (1-Sec)……….54 NW   @   08:35 A.M.
VECTOR #2 (1-Sec)……….52 NW   @   08:38 A.M.
DAVIS #1……………….53 W    @   04:54 A.M.
DAVIS #2 ………………49 W    @   04:45 A.M.
RMY #1 (Instantaneous)…..56 NW   @   08:35 A.M.
RMY #2 (Instantaneous)…..54 NW   @   08:38 A.M.
MERLIN…………………50 NW
RICHARDS (C5C) (Inst)…..OTS

FASTEST MILE:
CONTACTING ANEMOMETER/OFFICIAL………………34 NW   @   08:36 A.M.
MAXIMUM 2-MINUTE VECTOR #1 AVERAGE…………..34      @   08:39 A.M.
MAXIMUM 2-MINUTE VECTOR #2 AVERAGE…………..37      @   04:47 A.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………38 NW   @   08:39 A.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………38 WNW  @   04:47 A.M.
MAXIMUM 2-MINUTE RMY #1 AVERAGE……………..34 NW   @   08:39 A.M.
MAXIMUM 2-MINUTE RMY #2 AVERAGE……………..37 W    @   04:47 A.M.
MAXIMUM 2-MINUTE RICHARDS (C5C) AVERAGE……..OTS

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL……..19.2 NW [460 total miles] VECTOR #1………………18.0
VECTOR #2………………19.2
DAVIS #1……………….18.7 NW
DAVIS #2……………….18.8 NW
RMY #1…………………17.4 NW
RMY #2…………………18.6 NW
RICHARDS (C5C)…………..OTS

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M……..0.00 DEPARTURE…..-0.15
TOTAL PRECIPITATION FOR THE MONTH…………..2.62 DEPARTURE…..-0.70
TOTAL PRECIPITATION FOR THE YEAR (2025)…….13.33 DEPARTURE…..-4.01

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HRS ENDING 7 A.M…………..0.0 DEPARTURE……-0.1
TOTAL SNOWFALL FOR THE MONTH………………..1.7 DEPARTURE……-0.9
TOTAL SNOWFALL FOR THE SEASON (2024-2025)……35.8 DEPARTURE…..-33.7

————————————————————–

PRELIMINARY CLIMATE SUMMARY FOR APRIL 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

4/1    55/32/44/+3/0.17/0.0/512/67       38 NW  VEC1 38 NW  RMY 40
4/2    42/27/35/-6/0.11/T/584/76         29 NNW VEC1 28 NNW RMY 29
4/3    62/32/47/+5/0.31/0.0/000/00       38 SW  VEC1 38 SW  RMY 39
4/4    69/47/58/+16/0.00/0.0/456/59      31 NW  VEC1 31 NW  RMY 30
4/5    47/36/42/-1/0.49/0.0/000/00       25 ESE VEC1 29 SE  RMY 25
4/6    51/37/44/+1/0.20/0.0/016/02       22 NNW VEC1 21 NNW RMY 21
4/7    45/34/40/-4/0.18/T/000/00         24 E   VEC1 23 NNE RMY 23
4/8    40/26/33/-11/0.10/0.1/196/25      51 W   VEC1 48 W   RMY 51
4/9    46/24/35/-9/0.00/0.0/755/96       36 WNW VEC1 33 NW  RMY 36
4/10   49/29/39/-6/0.01/0.0/569/72       23 SSW VEC1 23 SSW RMY 25
4/11   45/31/38/-7/0.39/1.2/024/03       25 ENE VEC1 27 ENE RMY 26
4/12   36/33/35/-11/0.46/0.4/000/00      39 ENE VEC1 40 E   RMY 42
4/13   42/35/39/-7/0.16/0.0/000/00       38 NE  VEC1 38 NE  RMY 40
4/14   67/35/51/+4/0.00/0.0/745/93       29 WNW VEC1 29 NNW RMY 28
4/15   66/44/55/+8/0.04/0.0/209/26       53 NW  VEC1 51 NW  RMY 54 TSTM
4/16   51/37/44/-3/T/0.0/484/60          44 WNW VEC1 43 WNW RMY 47
4/17   59/35/47/-1/0.00/0.0/…/..       35 WNW VEC1 34 WNW RMY 34
4/18   66/38/54/+4/0.00/0.0/…/..       41 SSW VEC1 42 SSW RMY 43
4/19   82/52/67/+18/T/0.0/…/..         40 WNW VEC1 40 W   RMY 40
4/20   67/45/56/+7/0.00/0.0/…/..       53 NW  VEC1 54 NW  RMY 56

4/21 The low since midnight is 37F, the daily normal low is 40F.

————————————————————–

APRIL DAILY RECORDS TO DATE

NONE.

————————————————————–

DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated)

RECORDS FOR APRIL 21
HIGH 85 IN 1923
LOW 22 IN 1908
PRECIP 3.18 IN. IN 1991
SNOWFALL 0.8 IN. IN 1947
PEAK GUST 76e MPH NE IN 1940

RECORDS FOR APRIL 22
HIGH 85 IN 1977, 2001
LOW 26 IN 1981
PRECIP 2.60 IN. IN 2019
SNOWFALL 3.0 IN. IN 1940
PEAK GUST 68e MPH NW IN 1945

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
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