Wednesday, August 07, 2013

Announcing End Of 90 Degree Weather For This Year Is Simply Premature

There's some hopeful speculation that the region avoids 90 between now and the end of the warm season.  It would be a very rare instance if that were indeed reality given it's only happened twice in the last 53 years -- 1963 and 1984 were the only two years since 1960 where Philadelphia avoided a 90 degree day after July 31st.

In fact, it's only happened six times since 1900 (1902, 1904, 1920, 1934, 1963, 1984).

Yes, most years feature at least one more 90 degree day in August...even in years where 90's are not all that common.

Since 1997, the average year features 8.5 more 90 degree days between August and September (the average is just over eight between 1981 and 2010).  Obviously "average" covers a wide expanse of numbers...we've had as many as 19 in 2010, 18 in 2002, and then three years since 1997 with just two.

Outside of a small chance at 90 on Saturday (upper 80's may be Philly's best hope at this point), it does look like the odds of a 90 degree day are low for the next couple of weeks. Modeling in the longer range does show a potential transition towards a warmer (at least to average) stretch forthcoming in late August, which would present a couple of chances at getting to or into the 90's.  The odds of a 2010 or even a 2007 type stretch where we rack up a bunch of 90 degree days from here on out looks unrealistic but even in years where we have had a wet June and/or wet July (1994, 1996, 2003) we've squeezed out a few more 90 degree days before year's end.

As our daylight starts to dwindle (we've already shaved off an hour from where we were in late June), the odds of getting above 95 are quickly dwindling -- if we were in a dry pattern this summer I would probably hold out some probability for 95+ before year's end but given how wet the region generally has been and how our soils are pretty moist overall, it's going to be tough to use the ground as an ally to get too hot.  The intense heat days are probably behind us for the summer but 90 or low 90's still remains a possibility at some point before the warm season concludes.