During a typical year, monthly average temperatures move steadily upward as spring progresses. Not so in 2012.
In a stunning reversal of the seasons, April 2012 averaged colder than March in numerous locations across the Midwest and Northeastern United States. An unprecedented March heat wave not only set thousands of daily high temperature records but also smashed monthly March temperature records by such a wide margin that April had nowhere to go but down.
Chicago, Buffalo, and Washington, D.C. (at Dulles Airport) were among some of the cities that accomplished this unusual feat. The March temperature at Washington-Dulles International Airport averaged 54.3 degrees, but fell slightly to 54.0 degrees in April.
Dulles was among several locations that had never before recorded a warmer March than April. In a press release from the Northeast Regional Climate Center at Cornell University, climatologist Jessica Rennells said:
A month later, March’s heat is still breaking records. March was warmer than April at 12 of our first-order stations. This is the first time for this to happen at Dulles, Scranton, Buffalo, Rochester, Syracuse and Binghamton since their record keeping began.
Related: Spring Backward? For Many, April Was Cooler than March (Climate Central)
Outside the Northeast, Chicago was perhaps the most notable location to defy the seasonal temperature trend. April averaged 50.7 degrees Fahrenheit in Chicago, which was already 1.8 degrees above the April norm* of 48.9ºF. Yet because the March temperature averaged 53.3 degrees – a record 15.6ºF above average – April ended up a cooler month by comparison. Andrew Freedman at Climate Central wrote last week that this has only once happened in Chicago’s weather history, back in 1907.
If daily temperatures normally move up and down, why is it so rare for April to average colder than March?
The reason is that we are referring to 24-hour temperatures averaged over an entire month. Just as daylight increases at its most rapid pace during March, so do average temperatures in many places.
Bucking the seasonal trend
A climate graph of Chicago to the right illustrates a fairly steep increase in the average monthly temperature from March through May. The average temperature increases by 11.2 degrees from 37.7ºF in March to 48.9ºF in April. In 2012, however, the April temperature fell 2.6 degrees, which is remarkable in the context of normal seasonal temperature trends.
Other cities in the Midwest and Central U.S. that saw April average cooler than March were Milwaukee, Columbus, and Omaha, Nebraska.
In Buffalo, N.Y. the normal monthly average temperature in March is 34.2 degrees. April averages 46.2ºF, some 12 degrees warmer. Yet in 2012, April averaged 2.2º cooler than March. Unlike Chicago, where April was the seventh straight month of above average temperatures, Buffalo actually saw a slightly cooler-than-average month (though only 0.7ºF below the norm).
In Washington, D.C. (the hometown of this blog), our official recording station at Reagan National Airport did not quite challenge seasonal trends, and indeed April averaged warmer than March as we would expect. Yet as mentioned above, nearby Dulles Airport joins other cities in the Northeast and Midwest that did experience an unprecedented cooler April than March.
The March temperature of 54.3ºF was Dulles’ warmest such month since records began in 1963 and the only time March ever averaged 50 degrees or higher.
Although April finished just slightly warmer than March at D.C.’s Reagan National Airport, local readers might be wondering: has Washington, D.C. ever experienced a cooler April than March in its 141-year climate history?
The answer is yes, twice - when the station was located at 24th and M St. in the District rather than Reagan National. Like Chicago, the first instance was in 1907, when March averaged 48.8ºF and April was 0.4 degrees cooler. More notable was 1921, when D.C. averaged 55.5ºF in March and averaged only 52.2ºF in April – a 3.3 degree drop!
Since records began at Reagan National Airport in 1945, April has never averaged a lower temperature than March. However, 2012 is still notable for having the smallest March-to-April temperature increase in D.C. history. In fact, the +1.5 degree difference in 2012 was one of only 3 years in which D.C.’s average April temperature was less than 2 degrees warmer than that of March (the other years were 1935 and 1936).
As for the other cities that saw spring take a step backward in April, May will certainly return to the normal order of things as summertime warmth is already here – if not just around the corner.
*All averages and norms are based on 1981-2010 climate data.