In the June heat wave, hospitals around the area say they handled dozens of dehydration cases. Most people aren't even aware they are headed for trouble.
Those who deal with heat stress say they aren't surprised of the trouble at training camp.
Dr. Richard MacKenzie, the chief of the emergency department at Lehigh Valley Hospital, says they've seen several heat-related illnesses this summer, and athletes are especially at risk.
Dr. MacKenzie told Action News, "It's the third leading cause of death of athletes across the nation - heat illness or heat stroke."
He says what puts athletes in greater danger is excessive exertion in the heat, paired with wearing heavy pads that don't always let their skin breath.
He says, "If you can't sweat you're going to get very hot, or if you sweat and it doesn't go evaporate, you're not going to do well."
We don't know all the details of what happened with Chris Clemons.
But even if athletes are drinking a lot of fluids, if they aren't used to the heat, that can get them in a lot of trouble.
And many of us have a false sense of whether we are heat-ready.
As Dr. MacKenzie says, "For most of us, living in air conditioned surroundings, and sitting inside, we're really not very acclimatized to the heat. We are somewhere in between."