Some managers are pretty lazy and useless. I've only had one manager that I really respect for the amount of effort they apply to their position.
It does get REALLY hot and REALLY COLD in the terminal. I've come close to passing out while loading trucks before in the summer. They do provide juice/water on these hot days, but still, it's flippin hot. The terminal I was at before I transferred to my current one actually would not turn on the heat in the winter, so it was freakishly cold in the winter, and you couple that with sweating and it's just uncomfortable.
High turnover rate. If you're working at a bigger terminal, be prepared to see alot of people just walking out or quitting randomly, and leaving alot of slack for you to pick up. My advice for this situation is, just keep your mouth shut, stay optimistic, and just do the work. You'll receive recognition better this way.