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FPUS86 KSGX 012017 RRA
OPUSAN

DECEMBER WEATHER IN SAN DIEGO

WINTER AS WE KNOW IT IN SAN DIEGO GENERALLY BEGINS ABOUT THE
MIDDLE OF DECEMBER. EVEN THEN TEMPERATURES ARE MODERATE, THE
DAILY HIGH AVERAGING 64.7 DEGREES THE NORMAL LOW 48.4 DEGREES
AND THE MEAN 56.5 DEGREES ARE 4.8 DEGREES COOLER THAN IN NOVEMBER.
SINCE 1872 THE TEMPERATURE HAS DROPPED TO THE FREEZING POINT TWICE DURING
THE MONTH, ONCE IN 1879 AND AGAIN IN 1891, BUT HAS NEVER DROPPED LOWER.
ALTHOUGH THE HIGHEST READING WAS 88 DEGREES IN 1963 TEMPERATURES
ABOVE 80 DEGREES HAVE BEEN INFREQUENT.

THE NORMAL RAINFALL INCREASES TO 1.53 INCHES AND THE DAYS WITH
MEASURABLE RAIN AVERAGE 6.  HOWEVER MONTHLY TOTALS HAVE VARIED
WIDELY AND HAVE RANGED FROM NONE IN SEVERAL DECEMBERS TO 9.26
INCHES IN 1921. A TRACE OF SNOW FELL ONCE, ON DECEMBER 18, 1967.
IN SOME NEARBY LOCATIONS AMOUNTS OF A HALF INCH OR MORE SNOW
FELL AND REMAINED ON THE GROUND FOR AN HOUR OR MORE. ON A FEW
OCCASIONS STORM WINDS HAVE REACHED 40 MPH. IN 2004 A SPEED OF
58 MPH OUT OF THE SOUTH WAS REGISTERED ON THE 29TH WHICH
IS A RECORD FOR DECEMBER.

AVERAGE SUNSHINE IS 73 PERCENT OF POSSIBLE WHICH IS 2 PERCENT
LESS THAN IN NOVEMBER. CLEAR DAYS AVERAGE 14, PARTLY CLOUDY DAYS
AVERAGE 7, AND CLOUDY DAYS AVERAGE 10. THE AVERAGE NUMBER OF
DAYS WITH HEAVY FOG IS 4, BUT THERE IS A SUBSTANTIAL VARIATION
FROM YEAR TO YEAR.  DESPITE THE INCREASE IN RAINFALL, THE RELATIVE
HUMIDITY CONTINUES MODERATE WITH A MEAN OF 70 PERCENT IN THE
EARLY MORNING, 55 PERCENT NEAR NOON AND 58 PERCENT NEAR SUNSET.

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