not the hardest, but worst, was moving sprinkler line in Alfalfa in the summer. Like you the humidity was unbearable... we don't have high humidity but IN an alfalfa field, a wet one, the humidity sky rockets. I'd have to drink gallons, no exaggeration, of water a day.
Which leads me to this story... at work one day, moving sprinkler lines... there were 3 of us pulling and loading, then unloading, the lines and one driver on the tractor pulling the trailer. He was 'upper management'.
None of these guys I was working with, not even the driver, spoke a word of English. Well.... we ran out of water.
The driver had a full thermos. My co-workers hit the driver up for a swig of water... the driver refused... so we kept working but I could tell tension was growing. They hit him up again, (we were close to death from thirst).... no luck. The third time my co-workers asked for a drink the driver once again refused.... big mistake.
The two guys helping me on the ground went into a huddle... wasn't hard to figure out what they were talking about..... the driver, in mid-swig, was grabbed from behind, drug off the tractor, and got his ass beat. At which time the 3 ground guys, me included, satisfied our thirst.
I guess I was about 13-14 when this happened. - JamesJM