My wife did it for a few years and was at $19/hr. My sister did it a lot longer and made around $25/hr. People that do it for the full 25/30 years end up over $30/hr.
My wife and sister both did it in FL where it’s not quite as hot as AZ but a LOT more humid.
I was in the sign business and serviced electric signs on occasion. Some were big enough to crawl inside and it had to be 130-140 degrees inside.
A/C does no good in mail trucks because one of the windows is always open.
It’s more than that. If they get a few years seniority and work a lot of overtime which is common they can gross close to $500 daily, plus 30 days vacation and 10 paid federal holidays, health care, pension investments etc.