As we now know, meteorological winter (December through February) 2011-12 finished as the third warmest on record here in Washington, D.C.. Thinking back, warmth seems all too common around here, especially when one considers the last two summers were the hottest two on record.
The fourth warmest February on record to close our toasty winter can’t be a good omen going into the warm season, can it?
Well, there’s at least some potential good news if we examine the 20 warmest winters on record and roll them forward to the summer months of June-August. I can’t promise we’ll make up for missed snow during that time (joking!), but perhaps we’ll have fewer 90-degree days to tabulate than recent years.
Of the 20 warmest winters on record (prior to this winter), the average (and median) summertime temperature was 77.1 degrees, or just over a half a degree cooler the current 1981-2010 normal of 77.7 degrees. If this summer follows suit, that would make it the coolest by far since 2009, or roughly about 4 degrees cooler than the last two summers.
12 of the 20 warmest winters on record saw summer temperatures below the current normal of 77.7, and eight saw temperatures above normal. Two of those eight occurred in the 2000s and all occurred at the current observation location at National Airport.
Among those 20 warm winters, the warmest summer that followed averaged 79.4 degrees (1991 and 2002) or about two degrees above normal, and the coolest was 74.5 degrees (1890 and 1972) or about three degrees below normal.
All that in mind, there does seem to be at least a slight correlation between a warm winter and a warm summer considering all years on record (not just the warmest). However, examining only the winters over the last 50 years or so, the data exhibits no noticeable correlation.
When examining the graph above, we can remind ourselves that the last two scorching summers were preceded by significantly colder winters. In fact, this winter was 8.5 degrees warmer than the winter leading into summer 2010 and 7.6 degrees warmer than last winter (both of the last two winters were colder than normal).