I'm quite certain it's relative. Hydration and exercise are huge factors. I'm not sure how common it is now, but construction workers in hot climates were oft

I'm quite certain it's relative. Hydration and exercise are huge factors. I'm not sure how common it is now, but construction workers in hot climates were often given straight salt tablets to swallow in the past-- with as much water & exercise as they get, it's actually necessary to prevent Hyponatremia. They're probably more into energy drinks these days. Anyway, the person I was thinking of also seems to take in less fluids and get less exercise than I do on average, further compounding the difference for us in particular. That's part of why I mentioned our case, it's more extreme the closer you look.