Spring was warmest on record in Philly

May 2010 did not have quite the sizzle of 1991, when the temperature reached 90 or better 12 times -- 97 on the 31st -- but it was warm enough to add another record to an amazing weather year.

The average temperature for the March 1-May 31 period in Philadelphia, 58.4, was the highest ever for the period that constitutes the "meteorological" spring.

A footnote: The astronomical seasons are marked by the solstices and equinoxes, but the weather community breaks down the seasons into tidy three-month increments.

The 58.4 topped the 57.8 of 1921, a year when the temperature  hit 80 or better four times in March. It also nudged out 1991, with its July-like May.

What does this mean for the summer? Based on the record, probably nothing. The atmosphere sometimes exhibits the attention span of a gnat whacked by a windshield.

The fourth warmest spring, 1977, came after the coldest winter on record in Philadelphia. And after that toasty spring, the summer was on the cool side.

Although 1991 was one of the wamer summers on record, 1921 was decidedly middle of the pack.

In the early going, no particularly strong clues have emerged as to whether the next few months will be scorchers, but at least three different private services are calling for a hot August.

One factor that may argue against early heat is the rather amazing absence of drought across the contiguous United States.

As of last week, over three-quarters of the country was utterly drought-free. That's the biggest percentage in at least a decade.