For myself, younger me, I think I’d be more at 8 liters bicycling 20 miles. Young me commuted daily perhaps 5 or 6 miles at a gentle pace, peddling to work/school early morning, back in the evening.

Now on the other hand, a person in excellent physical health and fully acclimatized, well, had see it in person what I would assume from reading history and such.

Decades later, we had a staff member, probably in the range of 25 to 30 years old. His girlfriend later wife competed professionally in triathlons, a sponsored athlete. He did too, but not at a professional level.

His summer conditioning regime was simply bicycle commuting. From Awatukee, over South, up to Camelback and 24st. He changed clothes and shoes at the office. No hydration pack, think I remember water bottle, would guess he stopped at a drinking fountain somewhere in the South Mountain park.

Another anecdotal observation, my previous carrier had me driving to mountain tops. Here in desert Phoenix, South and Shaw specifically. I’ve unfortunately had to first responder a very few people at both, in the summer, typical potential newbie or out of towner, yep, I’ll be good midday hiking up Shaw Butte with my wee pint water bottle, suicidal idiots.

Contrast that with a fellow I’d see walking the South Mountain road, two WWII style canteens, moderate walking pace, looked like a mercenary. Summer, winter, always mid day - probably well conditioned physically. I compared him to my father in law, his biggest WWII gripe was walking across North Africa after being issued a wool uniform, army has a reputation then of sending exactly the wrong stuff to the troops. No hydration packs either.

My observation, I’m quite acclimated to this area, in that young me had no difficulty in 60F water for a swim, annual pulling the boat dock in standing in water that is beginning to ice over. Then after living in Phoenix a few decades, I didn’t last five minutes in summertime north Atlantic water.

Now that I’m old and the past 25 years an office worker, I seem to have the worst of both, can’t swim unless the water is warm, can’t go far mid day outside in the summer sun.

All these comments here about keeping cool and such, I appreciate the perspectives, but know the bottom line is acclimation and physical condition.

Stuck in the heat is uncomfortable, physically not dangerous if you are fit.