The union is calling out the school district for allowing students and staff to go to school on Monday despite having buildings without adequate heat.
A 6-month-old boy died after he was left in a hot car for about seven hours, authorities said.
Firefighters have to wear 40 pounds worth of gear when they respond, and they know the dangers of overheating.
Salim Wiggins was at the helm of a remote control lawnmower cutting the grass on some Philadelphia Water Department property in Strawberry Mansion.
Paramedics said they have been called to help people in all different age ranges, not just the very young and very old.
When it comes to preventative measures and staying hydrated, Dr. Liz Weinandy said, "the best way to avoid dehydration is to drink before you get thirsty."