Today on my route it hit 120 and I choose to not think what the temp was in the truck
This is the key. Once you start to focus on how hot or cold it is you are done.
That is not to say that you shouldn't take the proper precautions, to include hydrating before and during work, and taking advantage of air conditioned offices for a quick break from the heat.
It was in the low 90's here yesterday and it was hot but thankfully there was a breeze most of the day which made it feel a bit better. I had only 2 people ask me the really stupid "Hot enough for ya?" question.