The forecast mean              67% confidence           90% confidence
winter temperature is:             interval is:             interval is:

          36.8                       34.6 - 39.0               33.1 - 40.5

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.  A cold snap, for purposes of this forecast, was defined as a period of three or 
more consecutive calendar days when the temperature did not exceed 35 degrees. 

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