doesnt usually get too bad here, worst was last summer the hottest day of the summer I was doing an 8 yard mulch job it was 95 degrees out, left in the middle of the job to go to an apartment fire then came back and finished the job.
I get Gatorade and mix it in 1-gallon water jugs 50/50 with water. My old truck did not have A/C, but the new one does although I prob won't use it. I think its worse for your body to be in and out of the A/C all the time. Gotta hydrate BEFORE exertion too. So that doesnt mean wait til after your fisrt couple lawns to take a drink when you're thirsty. You need to start hydrating from the time you get home the night before.