Steady As She Goes
Having a warm April followed by a relatively cool May is not that uncommon...it's happened about one in every four years going back to 1968 and will likely happen again this year.What's interesting though is the magnitude of this month's cool weather when compared to the warm weather we had in April. If the month ended yesterday, the temperature increase from April to May would be the smallest in 136 years of recorded data in Philadelphia. The temperature increase from April to May is typically the largest of the warming months on the calendar as the monthly average temperature climbs 10.4 degrees from April (53.1 degrees) to May (63.5).
April 2008's average temperature of 56.3 only is 2.7 degrees cooler than this May's average temperature through Friday and with a week of the month left, it's possible we end up with a top 10 "coolest increase" in temperature between April and May. May 2008 is currently running 3.4 degrees below the average-to-date of 62.4 degrees so if we have "average" temperatures down the stretch we likely will end up in the middle to lower end of the top 10 on this list.
The current record for smallest April to May increase belongs to 1994, with a measly 3.0 degree increase and the most recent year that was in the ballpark was 2005, with 4.3 degrees warming between April and May.
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