July 30, 2025
Thom Carroll/for PhillyVoice
Philadelphia is experiencing another heat wave, with temperatures climbing into the high 90s this week. But according to apps and trackers, the 'real' temperature is in triple digits.
Another summer heat wave has roasted Philadelphia this week, with temperatures climbing into the high 90s. According to apps and trackers, the "real" temperature is even higher.
Weather services have long posted a second number alongside their air temperature readings, purporting to estimate what the conditions actually "feel like." It is often higher than what the thermometer reads in the summer, or lower in the winter. But it's not as quite as simple as the heat index, a figure that factors the relative humidity into the air temperature. Metrics like AccuWeather's RealFeel are a more complicated calculation.
"RealFeel or feels like are trying to incorporate, in addition to humidity, the sunshine, the wind," said Steve Decker, the director of the meteorology undergraduate program at Rutgers University.
As Decker notes, corporate weather services tend to use proprietary formulas that are guarded company secrets. But when calculating "real" temperatures, companies will generally consider cloud cover, the position of the sun and wind speed, among other components.
It's fair to expect lower readings, Decker said, when it's windier or cloudier. Conversely, a calm, bright day will likely have a higher "feels like" temperature. The time of day is another factor. It's hottest in the afternoon when the sun is at its highest in the sky and its rays strike more directly.
Coming up with a temperature estimate based on all these factors is subjective, Decker said, but they're "reasonable attempts" at gauging the weather as people actually experience it.
The latest heat wave is expected to break Wednesday night, but the city could feel "real" temperatures in the triple digits before that happens.
Follow Kristin & PhillyVoice on Twitter: @kristin_hunt
| @thePhillyVoice
Like us on Facebook: PhillyVoice
Have a news tip? Let us know.
