I had a similiar situation happen to me about 3 weeks ago. I had mowed the lawn one sunday afternoon in the heat, and didn't drink any water. The next day at work, I was fine until about 3pm and then all of a sudden I went downhill. It started with feeling dizzy and being light headed. I kept on working, even though I work in a shop with no a/c and fans that aren't worth a ****. Around 4:30, I started to throwup. I called my wife to come and get me and the car, since I knew I couldn't drive. She insisted on taking me to the ER because I was out of it, not coherent, and could barely walk. The ER took my vitals and rushed me right back to a room and hooked me up to a heart monitor. I was there around 6 hours with them monitoring my heart, pumping me full of fluids(2 bags), and some other medicine. THe doctor said it was definently heat exhaustion and more than likely a heat stroke but she said they weren't going to do the extensive tests to find out definite because of my age. I have a history of high blood pressure and after this incident it scared me, especially since I have a son on the way. Those of you who work in the heat or are just in the heat for a little while. Drink lots of water and gatorade, its not worth losing your life or getting really sick.
I usually don't like sharing stories about myself like this bc i don't want to look like a ***** but I figured this was worth sharing seeing what happened here and I had a firsthand experience unfortunantely.