Well regardless, firefighters have plenty of experience with running into hot as balls buildings and doing physically exerting things. If he wasn't referring to firefighters, then he should have been.
I was definitely thinking of Iraq because I'd say national guard are a pretty broad cross section of regular Americans, but firefighters, steel mill or industrial workers, etc are all highly relevant too.
Relatively extreme temps are an issue, but can be overcome. If it requires a couple weeks of practice for your staff to get used to working in 100-120f low rh environments but saves huge amounts of energy, it is worth considering.
In a cloud hosting environment, you could eventually have non safe temperatures in active operation, lots of redundancy, and just do all your human maintenance during reduced power/temp windows all at once. Sort of like treating the data center as the inside of a computer. Either run multiple facilities or partition by thermal suite or hae the equipment power management be able to throttle cores for reducing heat.
