I've worked outdoors my entire life. Last month was the first time ever I've had any problems overheating....i guess that was what it was. We took the children to a theme park for two days. I felt fine. The next day, I woke up and didn't feel very well, but went to work. As the day went on, I began to feel worse. I decided to come home, and on the way home I began to shiver; more like convulsing uncontrollably. In 100 degree heat, I drove home with the heat on full blast, still shivering. When I finally got home and got out of the truck, everything turned dark, and I had to sit down a few minutes before continuing into the house. I put on a heavy coat, turned the air off, and got into bed under the covers and laid there until late the next day. I felt a bit better then, but it took about a week to get back to normal. As I said, this has NEVER happened to me, and I stayed hydrated; I thought. I never felt bad until the following day. I also found it odd that my wife and kids had no ill effects.