Foolish me: I decided that I didn't want to miss my daily workout, and not having access to a gym, I figured that a walk would be a good alternative. I didn't walk fast, but long -- 1-1/2 hours. Unfortunately, I did this at the hottest time of day, though I didn't realize it was a problem at the time. But during this walk, I drank 3 bottles of water. When I returned to the house, I drank another bottle of water. I felt fine.
About 3-4 hours later, shortly before I needed to get dressed for the bar mitzvah, I stopped in at Best Buy in Aventura to buy a new power cord for my laptop, as my power cord was failing, and I knew I wouldn't make it home with access to my computer without it.
Suddenly, I felt very dizzy. It didn't help that the sales person I asked for assistance just pointed toward a wall and said "Over there." I headed for customer service, and by then I was ready to pass out. They weren't particularly interested, but one girl found a bottle of cold water and gave it to me. I drank it, but felt no better.
It was about an hour before I felt it was safe to stand up. During this time, I called my son, who was just leaving a job interview, to come get me. He drove up with food (that he made me eat even though I told him I had eaten and wasn't hungry) and a few more bottles of fluids. (He's very protective).
I was fine the next day, but I did miss the bar mitzvah... However I get to go back again next month for my niece's wedding, and I will NOT exert myself except under air-conditioned conditions!