Climatological Report (Monthly)
Issued by NWS Portland, ME

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CLIMATE REPORT
NATIONAL WEATHER SERVICE GRAY ME
548 AM EDT FRI JUN 02 2023

...................................

...THE PORTLAND ME CLIMATE SUMMARY FOR THE MONTH OF MAY 2023...

CLIMATE NORMAL PERIOD: 1991 TO 2020
CLIMATE RECORD PERIOD: 1941 TO 2023 (FOR TEMPERATURES)
CLIMATE RECORD PERIOD: 1871 TO 2023 (FOR PRECIPITATION)
CLIMATE RECORD PERIOD: 1882 TO 2023 (FOR SNOWFALL)

WEATHER         OBSERVED          NORMAL  DEPART   LAST YEAR`S
                VALUE   DATE(S)   VALUE   FROM     VALUE DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH             94   05/31/1987
 LOW              23   05/09/1956
HIGHEST           89   05/28         84       5       84  05/14
LOWEST            30   05/18         32      -2       31  05/09
AVG. MAXIMUM    66.4               64.2     2.2     65.1
AVG. MINIMUM    43.6               45.5    -1.9     46.3
MEAN            55.0               54.9     0.1     55.7
DAYS MAX >= 90     0                0.4    -0.4        0
DAYS MAX <= 32     0                0.0     0.0        0
DAYS MIN <= 32     1                0.7     0.3        1
DAYS MIN <= 0      0                0.0     0.0        0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM       12.34   2006
 MINIMUM        0.49   1965
TOTALS          3.94               3.67    0.27     1.12
DAILY AVG.      0.13               0.12    0.01     0.04
DAYS >= .01        8               12.5    -4.5        6
DAYS >= .10        6                7.1    -1.1        4
DAYS >= .50        2                2.5    -0.5        1
DAYS >= 1.00       1                0.7     0.3        0
GREATEST
 24 HR. TOTAL   3.06   04/30 TO 05/01

SNOWFALL (INCHES)
RECORDS
 TOTAL           7.0   1945
TOTALS           0.0                0.0     0.0      0.0
SINCE 7/1       56.5               68.7   -12.2     44.1
SNOWDEPTH AVG.     0
DAYS >= TRACE      0                0.0     0.0
DAYS >= 1.0        0                0.0     0.0
GREATEST
 SNOW DEPTH        0
 24 HR TOTAL     0.0


DEGREE DAYS
HEATING TOTAL    308                325     -17      292
 SINCE 7/1      6131               6705    -574     6400
COOLING TOTAL      6                 10      -4       11
 SINCE 1/1         6                 11      -5       11
................................................................

WIND (MPH)
AVERAGE WIND SPEED              9.2
HIGHEST WIND SPEED/DIRECTION    33/110    DATE  05/01
HIGHEST GUST SPEED/DIRECTION    50/110    DATE  05/01

SKY COVER
AVERAGE SKY COVER           0.36

AVERAGE RH (PERCENT)     61

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              0     HEAVY RAIN                 2
RAIN                      5     LIGHT RAIN                 8
FREEZING RAIN             0     LT FREEZING RAIN           0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     FOG                        8
FOG W/VIS <= 1/4 MILE     2     HAZE                       1

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

&&

THE COOL, CLOUDY, AND DAMP PATTERN THAT DOMINATED THE SECOND HALF OF
APRIL PERSISTED INTO THE FIRST WEEK OF MAY. A SIGNIFICANT RAIN EVENT
THAT STARTED ON APRIL 30TH CONTINUED INTO MAY 1ST WHERE THE PORTLAND
AREA RECEIVED 3.06 INCHES OF RAIN WITH UPWARDS OF 5 TO 6 INCHES
FALLING ACROSS THE MOUNTAINS AND CENTRAL MAINE LEADING TO
SIGNIFICANT FLOODING. THE PORTLAND AREA WENT ON TO RECORD MEASURABLE
PRECIPITATION FOR THE NEXT FOUR DAYS OF THE MONTH WITH TEMPERATURES
AVERAGING BELOW NORMAL. THE BLOCKING PATTERN ASSOCIATED WITH THE
NEGATIVE PHASE OF THE NAO WAS RESPONSIBLE FOR THIS PROLONGED PERIOD
OF DREARY WEATHER, AND THIS PATTERN BROKE DOWN BY THE END OF THE
FIRST WEEK OF MAY. A PERIOD OF DRY WEATHER ENSUED, AND WITH THE
EXCEPTION OF A COUPLE COOL DAYS AND SEASONABLY COLD NIGHTS,
TEMPERATURES AVERAGED ABOVE NORMAL THROUGH THE MIDDLE OF THE MONTH.
TOWARDS THE END OF THIS DRY STRETCH OF WEATHER A COLD FRONT CROSSED
ON THE 17TH WITH A CANADIAN HIGH PRESSURE SYSTEM BUILDING IN BEHIND
THE FRONT. THIS HIGH ALLOWED FOR STRONG RADIATIONAL COOLING WITH THE
LAST FREEZE OF THE SEASON OCCURING ON THE MORNING OF THE 18TH WHEN
THE LOW TEMPERATURE DROPPED TO 30 DEGREES. A COUPLE DAYS LATER, A
COASTAL LOW PRESSURE SYSTEM MERGED WITH A COLD FRONT APPROACHING
FROM THE WEST BRINGING SIGNIFICANT RAINFALL TO THE PORTLAND AREA
WHEN A STORM TOTAL OF 2.33 INCHES FELL ON THE 20TH INTO THE 21ST.
COOL WEATHER FOLLOWED THIS HEAVY RAIN EVENT BEFORE A RIDGE OF HIGH
PRESSURE BUILT IN OVER THE NORTHEAST RESULTING IN VERY WARM WEATHER
TO CLOSE OUT THE MONTH OF MAY.

THE AVERAGE TEMPERATURE FOR THE MONTH WAS 55.0 DEGREES, WHICH WAS
0.1 DEGREE ABOVE NORMAL. THE WARMEST MAY ON RECORD WAS IN 2015 WHEN
THE AVERAGE TEMPERATURE WAS 59.5 DEGREES. THE COOLEST WAS IN 1967
WHEN THE AVERAGE TEMPERATURE WAS 47.2 DEGREES.

A TOTAL OF 3.94 INCHES OF PRECIPITATION FELL, WHICH WAS 0.27 INCHES
ABOVE NORMAL. THE WETTEST MAY ON RECORD WAS IN 2006 WHEN A TOTAL OF
12.34 INCHES OF RAIN FELL. THE DRIEST WAS 0.49 INCHES IN 1965.

THE FOLLOWING DAILY RECORDS WERE SET OR TIED IN MAY 2023...
DATE   RECORD                                PREVIOUS
MAY  3    4   - LOWEST TEMPERATURE RANGE      4 IN 1998 AND OTHERS
MAY 18   30   - COLDEST LOW TEMPERATURE      31 IN 1981 AND 1959

$$

DS


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