Monday, September 22, 2025

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

MONDAY, SEPTEMBER 22, 2025
ALL TIMES ARE IN EASTERN STANDARD TIME (EST)
SUNRISE: 0532E
SUNSET:  1741E

A MIX OF SUN AND CLOUDS WITH A BIT HIGHER HUMIDITY AND WARMER
TEMPERATURES ON THIS FIRST DAY OF ASTRONOMICAL AUTUMN….

As we enter the Autumnal Equinox this afternoon, a bit more of
a summery feel will greet us over the next couple of days.
Today is featuring a mix of sun and clouds with temperatures
warmer than they have been the past couple of days. Humidity
levels are also a bit higher today, but all in all it’s still
fairly pleasant for this time of year.

Temperatures started the day in the low to mid 50s here on the
summit, but did dip into the 40s in the lower surrounding areas.
Readings have rebounded nicely into the low 70s by early this
afternoon, which is a touch above normal for the date. Dew point
values have been generally in the mid 50s, so while it’s a bit
more humid than the past couple of days, it’s still at rather
comfortable levels for the time being.

Today is yet another day to feature a light wind. The average
speed for the day so far is only around 6mph. The peak gust
is 16mph so far, which occurred just after 11am this morning.

Visibility has generally been between 30-50 miles for most of
the day today.

The maximum temperature so far today is 73F degrees, which is
3 degrees above the normal high of 70F. The minimum temperature
since midnight is 53F degrees, which is equal to the normal low
of 53F.

————————————————————–

Today’s Observations:

7 A.M.
Weather: Broken cirrus, few stratocumulus distant ENE-SE,
few altocumulus/castellanus distant SW-NW-NNE
Temperature: 58F; Dew Point: 55F; Relative Humidity: 89%
Wind: ESE @ 3 kts, wind light
Sea-level pressure: 1023.1 mb; 30.21 in. Hg: rising, then steady
Visibility: 30 miles
6-hr Max temp: 58F
6-hr Min temp: 53F
24-hr Precip: 0.00 inches
BHO SA 1155 E250 BKN 30 231/58/55/1103/021/ FEW SC DSNT ENE-SE
FEW AC/ACC DSNT SW-NW-NNE PTCHY GF SE/ 8/581 51004 10058 20053

10 A.M.
Weather: Broken cumulus, broken cirrus
Temperature: 65F; Dew Point: 56F; Relative Humidity: 72%
Wind: SW @ 5 kts, wind light
Sea-level pressure: 1022.9 mb; 30.21 in. Hg: steady, then falling
Visibility: 40 miles, hazy
3-hr Precip: 0.00 inches
BHO SA 1455 E20 BKN 250 BKN 40 229/65/56/2205/021/ HAZY WND LGT/
8/201 58002

1 P.M.
Weather: Thin scattered cirrus, few cumulus all quadrants
Temperature: 71F Dew Point: 53F; Relative Humidity: 54%
Wind: SSW @ 7 kts
Sea-level pressure: 1020.6 mb; 30.14 in. Hg: falling, then more slowly
Visibility: 50 miles
6-hr Max temp: 73F
6-hr Min temp: 58F
6-hr Precip: 0.00 inches
BHO SA 1755 250 -SCT 50 206/71/53/2107/014/ FEW CU ALQDS/
8/201 56023 10073 20058

————————————————————–

SUMMARY FOR SUNDAY, SEPTEMBER 21, 2025

TEMPERATURE (DEGREES F)
MAX…….68   NORMAL…..71
MIN…….52   NORMAL…..54
MEAN……60   NORMAL…..62

DEPARTURE FROM 30-YEAR (1991-2020) NORMAL…………….-2
TOTAL DEPARTURE FOR THE MONTH………………………-17 [-1.0 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON: JUL 2025 THRU JUN 2026)
TOTAL HEATING UNITS FOR YESTERDAY……………..5  DEPARTURE……..+1
TOTAL HEATING UNITS FOR THE MONTH…………….37  DEPARTURE…….-10
TOTAL HEATING UNITS FOR THE SEASON……………57  DEPARTURE……..-8
TOTAL HEATING UNITS LAST SEASON TO DATE……….33  DEPARTURE…….+24

COOLING DEGREE DAYS (SEASON JAN 2025 THRU DEC 2025)
TOTAL COOLING UNITS FOR YESTERDAY……………..0  DEPARTURE……..-2
TOTAL COOLING UNITS FOR THE MONTH…………….38  DEPARTURE…….-27
TOTAL COOLING UNITS FOR THE SEASON…………..710  DEPARTURE…….+49
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)………..18 ESE  @   05:09 P.M.
VECTOR #1 (1-Sec)……….19 SE   @   04:49 P.M.
VECTOR #2 (1-Sec)……….17 ESE  @   05:10 P.M.
DAVIS #1……………….17 ESE  @   05:09 P.M.
DAVIS #2 ………………18 SE   @   05:10 P.M.
RMY #1 (Instantaneous)…..19 ESE  @   05:09 P.M.
RMY #2 (Instantaneous)…..18 ESE  @   05:10 P.M.
MERLIN…………………16 SE
RICHARDS (C5C) (Inst)……17 SSE  @   09:56 P.M.

FASTEST MILE:
CONTACTING ANEMOMETER/OFFICIAL………………13 SSE  @   10:23 P.M.
MAXIMUM 2-MINUTE VECTOR #1 AVERAGE…………..13 SSE  @   09:59 P.M.
MAXIMUM 2-MINUTE VECTOR #2 AVERAGE…………..13 ESE  @   05:10 P.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………13 ESE  @   05:10 P.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………14 SSE  @   05:11 P.M.
MAXIMUM 2-MINUTE RMY #1 AVERAGE……………..13 ESE  @   05:10 P.M.
MAXIMUM 2-MINUTE RMY #2 AVERAGE……………..13 ESE  @   05:10 P.M.
MAXIMUM 2-MINUTE RICHARDS (C5C) AVERAGE………13 ESE  @   05:10 P.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL………5.8 SE [140 total miles] VECTOR #1……………….6.4
VECTOR #2……………….6.8
DAVIS #1………………..6.3 SE
DAVIS #2………………..6.3 SE
RMY #1………………….6.1 ESE
RMY #2………………….6.8 ESE
RICHARDS (C5C)…………..6.9

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…..-0.13
TOTAL PRECIPITATION FOR THE YEAR (2025)…….33.91 DEPARTURE…..-3.41

————————————————————–

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  67/51/59/-4/0.00/…/..            20 SE  VEC1 19 SE  RMY 18
9/21  68/52/60/-2/0.00/…/..            18 ESE VEC1 19 SE  RMY 19

9/22 The low since midnight is 53F, the daily normal low is 53F.

————————————————————–

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 22
HIGH 90F IN 1895, 1914
LOW 30F IN 1904 (Earliest freeze)
PRECIP 1.16 INCHES IN 2001
PEAK GUST 60 MPH SSW IN 1989

RECORDS FOR SEPTEMBER 23
HIGH 93F IN 1895,1914
LOW 33F IN 1904
PRECIP 2.67 INCHES IN 1994
PEAK GUST 62 MPH SSW IN 1989

TODAY’S REPORT PREPARED BY: Matt Douglas