I ran yesterday late morning, totally exposed for a few hair shy of 8 miles. I was thinking on a rolling hill the last mile, my god, this is awful. I slowed my pace to about 10:30 and just took it as a cool down mile to avoid totally redlining. I checked the dew point after I got home and cooled down. 72 dew point, give me altitude any day over that bs. When I've talked to runners who have trained or live at altitude, they adapt much sooner than any of us ever adapting to high humidity/dew point. There's no adapting happening, it's just survival lol.