Philadelphia is under an extreme heat warning with heat index values up to 105 degrees, advising residents to stay cool and hydrated.

The National Weather Service warns this could be the most intense heat in over a decade, with little nighttime relief as temperatures remain between 75-80 degrees.

If Tuesday's heat felt unbearable, you're not imagining it. Boston hit 102 degrees, the hottest June day in the city since 1872, according to the National Weather Service. That kind of heat is incredibly rare in New England,