Wednesday, September 18, 2013

Earliest Sub 50 Degree Low In Philly Since 1990

With this morning's crisp start in Philadelphia (low of 48 this morning), thought I'd pull out the dustbin of yore to compare morning lows of the past to see how long it had been since we had a morning low in the 40's any earlier in the "cool" season.

It's been 23 years -- September 18th, 1990 -- since we've had an earlier sub 50 degree morning. The low that morning was 44 in the city. That's not a record, for what it's worth...that mark is 42 degrees set back in 1959.

The list on the left shows morning lows in the 40's for any date in August and September on or before 9/24 since 1985 -- we went through a cool stretch in the 1980's with some August 40's and earlier September 40's strewn in through 1985 and 1986.

The last sub 50 degree morning in September in Philadelphia occurred on September 30th, 2006 at 47 degrees.

In terms of "numbers by decade" of sub 50 degree mornings in September (and August in the 1980's), Philadelphia had eight total mornings below 50 in the 2000's, 22 in the 1990's, 42 in the 1980's, and 23 in the 1970's.  Given that some 'warm' winters like 1972-3, 1974-5, 1991-2, and 1997-8 populate the list alongside colder winters like 1980-1, 1985-6, and 1993-4, there isn't any correlation between early chill and winter performance.  This isn't any more a harbinger of a bad winter than a 90 degree day in May is of a hot summer.

It is, however, an increasingly rare treat for the region, one that few will complain about and a nice contrast to those 90 degree temperatures we had a week ago.