Saturday, April 28, 2012

No Huge Shift

March 2012 was one of the warmest on record but April 2012, thanks to its cool finish, is turning out rather pedestrian. While temperatures will likely end up above average for the month by the time all is said and done, its increase in average temperature from March to April is shaping up as one of the smallest on record in Philadelphia.

Going back to 1872, this April is shaping up as the first since 1946 where we have seen such a close temperature spread between the preceding month and this month.  The difference through yesterday of 3.9 degrees is the closest spread since 1946's two degree spread between March and April.   Depending on positioning at the end of the month, this will either be the fifth or sixth closest spread in temperature -- 1903's 3.8 degree spread lurks at #5.

Of the six closest spreads between March and April temperature, five of the years featured a top ten warmest March...only 1874 did not feature one of the warmest Marches on in fact finished 1.4 degrees below the historical all-time average March temperature (42.1).  The 1874 spread was intriguing...not only did April 1874 finish as the coldest on record (an average of 10.2 degrees below the all-time average of 52.6), it also featured nearly ten inches of precipitation, which is still a record.  In fact, April 1874 likely featured at least some snow on a couple of occasions but our current climate record for snows only goes back to 1885.

The largest shift between months occurred in 1885 -- March's temperature of 30.8 (coldest on record) rebounded to an April reading of 50.6...a shift of 19.8 degrees between months.  We haven't seen anything close to that around here since 2005 when March's average of 39.5 rebounded to 55.3 in April, an increase of 15.8 degrees.