Me too but in Orlando FL, around 88 degrees. I finished my 20 mile bike ride, got back to the car, splashed some water in my face and ate a gel block or shot block. Then five minutes later I started having a rapid heartbeat and I got really scared about it to the point that I hyperventilated a little bit and thought about stopping the car. I said to myself, calm down, drink more water and wait until the block gets through your system. And yes, a few minutes later I was fine. But have been wondering if rapid heartbeat is a sign of heat injury. Hmm...