Framing The Hot Talk Around Reality

What constitutes as "hot" and "heat wave" can be entirely subjective and at times the usage of both terms can lead to some discussion and debate over what's really a heat wave, what isn't, and what is hot and not.   There are truly hot days, such as Monday and Tuesday, as the combination of heat and humidity brings a higher temperature to the region and has it feeling much, much warmer than what the publicized air temperature is.   At the same time, there are days such as Sunday, when the high temperature is 90 degrees and the heat index is the same, perhaps lower, than the temperature.   Would have considered a day like Sunday hot? 

The "beauty" is in the eye of the beholder.

Let's first tackle "heat waves" since there is a clearly defined (whether you like it or not) approach to it.  In Philadelphia, the gold standard to measure "heat waves" is three or more days of high temperatures of 90 or higher, regardless of heat index.   While a three day heat wave in April (when the average high is in the upper 60's) or October (low 70's) is much more impressive than a three day heat wave in July (average high of 87), the definition is consistently applied throughout the year.   One of the big reasons for a clearly defined mark for heat waves in Philadelphia is the lack of air conditioning in many Philadelphia homes.    As many homes in the city are made of brick, heat radiating into the buildings effectively turns them into ovens...while you can't bake a pizza in a brick oven home, a person can bake to death.   The row home effectively becomes a death trap as temperatures rise inside the house to above 90, even on the ground level, at which point fans become ineffective.   While the numbers of homes in the city without air conditioning has decreased in recent years, a good number of the city's poorest and elderly still lack air conditioning.

The July 1993 heat wave in Philadelphia resulted in 118 deaths as temperatures climbed to 100 or 101 for three straight days and 90 or above for eleven in a row.   That heat wave is one of the more deadly in our nation's history and it drove a good deal of research among meteorologists and medical professionals to find preventive causes and measures to lower heat fatalities.   As a result, the heat advisory and warning system that we're used to seeing locally was pioneered here in the Delaware Valley by the National Weather Service and was used in a heat wave that blasted the region two years later.   Temperatures were quite hot (25 straight days of 89 or higher, 24 of them at/above 90) but the fatality level that year dropped to 72 despite a longer duration of heat compared to the '93 event.   

Those of us with air conditioning may think the "90 degree = hot" meme is a bit low, especially in July and that  using 90 as the definition for a heat wave is a bit low, especially in July.   However, that lack of air conditioning for the city's poorest is an issue and does lead to more sensitive reactions in the media...and perhaps justifiably so.

Whether we should redefine "hot" to a higher standard (mid 90's in midsummer, 90 before Memorial Day and after Labor Day) and whether the heat wave definition should change as well is sometimes up to debate.  I'm not convinced changing the heat wave definition on temperature locally is a good idea -- the city has essentially lived with 90 and three days as the definition of a heat wave for a while and has had this definition going back to prior to the '93 heat wave.    While three straight days with high temperatures of 90 or 91 constitutes a rather "cheap" heat wave in July for many, it still is rather warm for those who are outside all day or those who lack air conditioning.    Perhaps we extend the definition of heat wave to four days of 90 or higher?   This might help on the "cheap" heat waves but it doesn't necessarily capture the scope of a heat spike where temperatures for a couple of days are in the mid or upper 90's.  

One consideration is to develop an "ugly" scale for heat/humidity/duration, one that assigns points based on temperatures above 90, consecutive days, and departure from average.     If a particular threshold is crossed, you have yourself a heat wave?   Would be far more confusing than the current definition but it certainly would be good to use in comparison of "ugly" historically...much like the WAR statistic in baseball or PER in basketball, which are metrics that stataholics have developed to measure players to each other.

Given our climate in summer (July's average high is 86, 87 degrees), we'll probably always have the heat debate flare up from time to time in the heat of summer.  While heat is definitely subjective as some of us have higher tolerance of heat than others, I think the heat wave definition is one that...at least for now...should be left as it is.   While it's not perfect, it at least provides a clear definition that many can understand as many folks do think 90 is hot, regardless of the time of the year.