the temperature all day was around 100F, what benefit/s if any does training in extremely high temperature have for the body? i know it can build mental toughness, assuming you can control effort, sustenance and get home.
I'm currently minoring in sports medicine and training in heat does nothing for you other than break your body down faster and put you in danger faster. It does however offer you a placebo effect like "oh it can't get any hotter than today. If you are training in the heat remember to rehydrate every 45 minutes and probably invest in some salt tabs to replenish the large amount of salt you will be losing.
Like many potentially performance enhancing strategies, heat acclimatisation is all about being intelligent and knowledable regarding what you are doing and what you want to achieve from it. If your goal is to improve performance in the heat, there is no doubt that a properly done heat acclimatisation intervention IS beneficial. If your goal is to improve performance in thermoneutral conditions, there are a number of physiological adaptations such as increased plasma volume and an increase in heat shock proteins, that may lead to enhanced performance. But as others have already noted here, if you over do it, then you simply increase the overall stress on the body which can lead to maladaptation instead of a positive response.
For the record, without wanting to come across as a big headed know-it-all or anything, I do actually have a PhD in exercise physiology and many yrs experience working with elite athletes
I don't know if it does you any good. I am in Texas and it's hot in the summer. I have gotten to where I sort of enjoy the heat. I was riding for about 2 hours in it this afternoon. It's better than not riding - or using the stationary bike!