AskHistorians

Obviously in movies clothing looks better than it likely did in daily life, which during the “old west” time period would be typically dirty, highlighted with more dirt.

Folks were lucky who had two sets of clothes- most folks had one set and that would include most hired cow hands. Some top men may have two. Three would mean you are very well off.

Sometimes having clothes is better than not in dry heat, as it will protect your skin from the direct sun, and sweat will still evaporate to cool you.

Having a rag or bandana to breathe through when dust/sand is kicked up by livestock translates a bit into the western wear theme as well.

Humidity is different, but the West is usually dry.

Plus it wasn’t quite as hot as it is now.

Men died more back then from everything, so it’s reasonable to believe that many did die from heatstroke, especially in areas where water is in short supply.

But it’s also true that humans are highly adaptable and most of these men were working and living outside, day after day, week after week. They had never felt air conditioning so were likely not in as much discomfort as a soft American would be.

These men often did not lead long lives, and often only did ranch hand work until they could make enough to start their own homestead or business or family. Some were criminals, some just started out poor - think of it as the factory job of that time period. Anyone could learn it- a few were good at it and moved up or started their own ranches.