|The forecast mean winter temperature is:||67% confidence interval is:||90% confidence interval is:|
|33.7||31.5 - 35.9||30.0 - 37.4|
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 2007/08 that came from PHL. It was found that the combination of the extended Julian date (beyond 365 or 366 after December 31) 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.
For purposes of this forecast, a cold snap is defined as at least three consecutive days when the temperature does not exceed 35 degrees.