Tuesday, July 24, 2012

Updating July's Hot Flash

With the very hot star to July there was speculation that this July could ultimately exceed last July's record setting temperature average for the month. Looking at temperature trends in computer modeling over the next seven days, I'm not sure that will ultimately be the case.

Through yesterday, Philadelphia's average temperature was 82.0 degrees, about a tenth of a degree behind the pace that we were at through July 23rd of last year (82.1 degrees)...when the rest of July 2011 was buoyed by five 90 degree days in the final eight days (including highs of 98 and 96) to boost the monthly average to 82.4 degrees.

Our temperature trend over the next seven days doesn't call for such a persistent and consistent run of heat through month's end...although a few flirtations or days of exceeding 90 are definitely possible.  

The chart of hottest months of July in Philadelphia's history shows that 2nd place is currently held by 1994 -- 82.1 degrees.  That might be our hottest case scenario for where we finish...somewhere close to 1994's mark for the month as temperatures look to close out on a relatively consistent keel to our monthly average.  Whether we're 2nd or 3rd is an academic exercise at this point...it would be the third straight summer with a top five July in terms of heat...something that we last experienced in the mid 1990's when 1993, 1994, and 1995 were the prior "gold standard" hot summers and took the top spots in a three year succession, with 1994 the hottest of the bunch prior to this three year run.

For those curious about how the averages of the 93-95 run played out to the averages of the recent three years, the data shows our highs have been higher while lows haven't changed much.  Over the past three July's, the average high has been 91.2 degrees.  In the mid 90's run, the average high was 90.6.  Average nighttime lows the last three years were 72.8 degrees, in the mid 90's they were 72.7.  There hasn't been an appreciable rise in temperatures at night in the last three years although the daytime high spike has been over a half degree (which accounts for these last three years being in the current top four).