A week of high temperatures is upcoming in Philly, with heat indexes potentially over 100

After one of the warmest Junes in Philadelphia history, hot weather is forecast to continue over the next week, with a heat advisory in effect and heat indexes potentially surpassing 100 degrees.

A heat index is used to describe the “feel like temperature” or “apparent temperature,” said Ray Kruzdlo, a senior service hydrologist for the National Weather Service office in Mount Holly. By late afternoon, the high temperature for Monday had reached 95 degrees, while the forecast highs are 97 on Tuesday and 94 on Wednesday, though it will likely feel warmer.

The heat index could reach as high as 104, according to the National Weather Service’s heat advisory, which began at 10 a.m. Monday and is scheduled to continue until 8 p.m. Wednesday. The advisory could be extended if needed, Kruzdlo said.

“When you get this warm and your body is not used to it, it could be detrimental to your health,” Kruzdlo said.

In similar nature, the forecast UV index on Monday is 10 out of 11, and a 9 on Tuesday and Wednesday, which are categorized as “very high” according to the National Weather Service. The weather service advises people to stay inside if possible and take extra precautions like wearing light clothing and sunscreen when outdoors and by limiting outdoor activity.

The week is also expected to be a muggy one. Humidity will likely increase throughout the week, with potential thunderstorms starting as early as Wednesday, peaking on Friday, and scattering through Saturday, because of aftereffects of Hurricane Beryl, said Amanda Lee, a meteorologist in Mount Holly.

A relief in temperature is expected on Friday, but Saturday is again expected to reach as high as 90, with heat persisting into next week.

Heat advisories are issued differently throughout the country. A place like Florida wouldn’t have a heat advisory for the weather Philly is experiencing, as “they’re more acclimated to it,” Kruzdlo said. But during July in Philadelphia, the National Weather Service Office in Mount Holly will put out an heat advisory if heat indexes breach triple digits.

A heat wave is another term used differently throughout the country. In the Philadelphia region, the definition is loose, but oftentimes the National Weather Service will consider it is a heat wave when temperatures are above 90 for at least three consecutive days, Kruzdlo said.