Yes it has been cold but warmer weather is expected for a few days this week. Could this be a hint of the "January Thaw"?
This is not just a term, in fact there is a definition that can be found in the Glossary of Meteorology. A spell of mild weather popularly supposed to recur each year in late January in New England and other parts of northeastern United States.
Seems that this is not just a phenomenon that occurs in the Philadelphia area. Many areas found in the mid-latitudes in North America experience a warming that can last a week. The Average temperature for that week is 38 degrees, however during the thaw period it is not uncommon to see high temperatures about 10 degrees warmer than average.
There is no specific reason why this occurs and it does not occur every year. Glenn Schwartz and Jon Nese examine the thaw in the Philadelphia area Weather Book and can show a slight warming with the temperature data over the past 100 years. However they also state that if you were to analyze the statistics of the temperature data over the past 100 years you could prove that the thaw is just a random fluctuation (Nese, Schwartz).
Even if it can be explained as random, it still occurs and will be a welcome change this year from our cold windy weather. Even if it is for just a few days.
Ira W. Geer Editor. Glossary of Weather and Climate. American Meteorological Society, 1996
Jon Nese, Glenn Schwartz. The Philadelphia Area Weather Book. Temple University Press 2002.