This statement is false.  The Continental Army could not have spent the winter of 1777-1778 in Philadelphia in any conditions.  Philadelphia was, at that time, in the hands of the British.  The British (or at least their leaders, were comfortable in Philadelphia that winter,  By contrast, the Continental Army spent that winter in much less than comfortable conditions.  They spent the winter in camp at Valley Forge, PA.  This winter is famous for the fact that the Americans had to endure very harsh conditions.  The conditions were harsh enough that, as the link below tells us, a quarter of the troops were dead by the end of the winter.