Not a good way to lose water weight

I love to literally run errands. I don't know, there's just something fun about it. Yesterday I took my car to get the oil changed and today I ran the four miles to the dealership to pick it up. I got going a little later than I wanted to and saw a flashing sign that said 8:05 95 degrees.

The weather guy said it was supposed to rain this morning.

Anyhow, I got the story of the week at the dealership. The service guy said that he figured yesterday would be a great day to lose some water weight. So, he said, he threw on a sweatshirt and went outside and ran a mile and a half after work. Now, I don't know exactly what time he did this, but the high would have been at least 101 yesterday afternoon not counting the heat index.
This is unfathomable to me for two reasons: 1) a cotton shirt strikes me as a bit heavy right now. I love the sweat wicking fabrics. 2) I can't imagine running just one and a half miles. Today's four mile run seemed too short, even with the heat.
And here's the moral to his story. He didn't lose any weight because when he got back home he was drinking water all day long.

Tomorrow's high is only supposed to be 88 so that should be great weather for another 14 mile run sometime this weekend.