'F or what it's worth, under eight degrees is still potentially significant and still enough to create a different profile of human health risk. ' S ome cities are exposing considerable numbers of people to that 10 degree temperature departure because of the urban heat island effect,' said Peter Girard, vice president of communications for Climate Central, who includes Philadelphia in that category. Almost 194,000 residents, or 8%, experience an increase of 10 degrees or higher. Climate Central estimates that 18% of the population, nearly half a million people, experience an increase of 9 degrees or more. Some city residents suffer even greater temperature spikes. Free ways to beat the Philly heat as summer temperatures climb.The summer heat can cause an array of illnesses here's what to know.Temperatures to hit upper 90s in Philly region on Thursday and Friday.

It found that 38% of Philadelphians experience a temperature increase of 8 degrees Fahrenheit or more due to the effect, meaning that when it's 92 degrees outside, it really feels like 100. On Wednesday, the nonprofit released an analysis of the urban heat island effect, or the increase in temperature due to roads and other heat-absorbing infrastructure, in 44 major U.S. The urban heat island effect is making the scorching summer significantly hotter, according to new research from Climate Central.