Washington, D.C.’s official observing station at Reagan National Airport (DCA) finally recorded its first freeze of the 2012-2013 cold season this morning, dipping to 32. It was the 15th latest first freeze on record dating back to 1872.

The lateness of this freeze is surprising in light of the fact November - overall - has been significantly cooler than average. Through Sunday, the month’s average temperature was 3 degrees below normal. 14 or 26 days this month have dropped into the 30s at DCA but mainly in the mid-to-upper 30s rather than low 30s.

The colder than average temperatures but lack of freezing temperatures deep into November at DCA indicates there is increasing resistance in dropping into the low 30s. Urbanization and a long-term climate warming trend seem to both be playing a role in the later first freeze dates.

Ian Livingston and Justin Grieser documented a nearly two-week shift in average first freeze dates from the beginning of November to mid-to-late November since the mid-1940s when observations began at Reagan National Airport.

While DCA has struggled to dip down to freezing this cold season, most other spots in metro region have had little trouble, especially west of the beltway. For example, Dulles Airport has recorded 10 freezing days this month and 25 out of 26 days in the 30s or colder.


Here are the 15 latest first freeze dates on record at DCA since 1872:

15) 2012 11/26
13) 1958 11/27
13) 2002 11/27
12) 2010 11/29
11) 1979 11/30
10) 1948 12/1
8) 1983 12/2
8) 1985 12/2
7) 1975 12/3
6) 2004 12/4
5) 2009 12/6
3) 1978 12/10
3) 2011 12/10
2) 1980 12/14
1) 2001 12/22

Related: Washington D.C.’s first official freeze of the 2011-2012 winter, third latest on record

Ian Livingston contributed to this post