504 
FPUS86 KSGX 012041
OPUSAN

DECEMBER WEATHER IN SAN DIEGO

WINTER AS WE KNOW IT 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 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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DS