August was really weird weather the year we went. Usually Jan people and it's a consistent 25-31. August went from 36 to like 18 with heavy rain, and changed so fast the hot tub at Desire didn't adjust their temperature. Still a great time to go. I'd say more random weather than too hot/too cold.
You've been lucky then if your "hot" in august only got up to a high of 91F. We've been in August (let me look) four times, and there were two trips with more than one day's worth of 95-ish. But, you're right on target with the trade winds keeping things feeling comfortable. The issue is that, if you just stay right there near the Sexy Pool, or down in it, you don't get to feel the winds so that can get pretty steamy... especially for northern folks (like Minnesota, Canada, Wisconsin, Oklahoma... well, maybe not Oklahoma so much even though they're Northern too). But, coming from Houston, we're normally leaving 100F and ~99% humidity, so when we get to TTR it's like someone turned the outside A/C on...Houston feels like an armpit in August.
We've been in July a few times and it's hot, but the wife and I like hot. We will be there this August 18th. Haven't been back for years, because we did Isla with different friends our last Cancun trip, and then COVID ruined the last scheduled trip.
This makes us feel better. Going first week of August for 3rd trip but first around this time. Coming From New Orleans though so we understand that 100% humidity! Glad to hear it's better that the southern US heat.
