Winter, 2007/2008 Conditional Temperature Forecast
for Philadelphia International Airport in degrees Fahrenheit
  If the first cold    The forecast mean      67% confidence      90% confidence
  snap starts          winter temperature     interval            interval
  between:             is:                    is:                 is:
  
  December 1 - 15      34.6                   32.4 - 36.8         30.9 - 38.3
  
  December 16 - 31     35.3                   33.1 - 37.5         31.6 - 39.0
  
  January 1 - 15       36.1                   33.9 - 38.3         32.4 - 39.8
  
  January 16 - 31      36.8                   34.6 - 39.0         33.1 - 40.5
  
  February 1 - 14      37.6                   35.4 - 39.8         33.9 - 41.3 
  
  February 15 - 29     38.2                   36.0 - 40.4         34.5 - 41.9
  
  no cold snap         40.1                   37.9 - 42.3         36.4 - 43.8
Note: A cold snap, for purposes of this forecast, was defined as a period of three or more consecutive days when the temperature did not exceed 35 degrees.

The normal winter temperature at PHL is 34.8 degrees.

The above forecast is from a multiple linear regression equation that was derived from data from 1950/51 through 2006/07 that came from Philadelphia International Airport (PHL). It was found that the combination of the extended Julian date (beyond 365 or 366 after December 31st) of the first cold snap of the season, the October mean minimum temperature, and the November mean maximum temperature explained approximately 47 percent of the variance in mean winter temperatures.

Winter is defined as meteorological winter, i.e., the months of December through February.

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