Through Monday, temperatures for 2013 are averaging out to 69.2 degrees, or 1.3 degrees below average for this time of the year. It's also the fifth coolest September in the last 20 years as well.
The warmest September in recent years was 2005, averaging 75.6 degrees in the first 23 days. It also ended up averaging out to the third warmest on record before all was done (73.8 for the month).
If you look at the temperature trends of September...just like the morning lows...there is little correlation to the proceeding winter. While 2009 was a cool September and a cold winter, 2006's cool September gave us a very warm first half of winter and a warm winter overall. 2010's warmth preceded a cold winter. So, September recently doesn't matter much. There are better harbingers of winter that reside in October temperature and in weather patterns that begin to evolve in the coming weeks.