If you don't already have one, consider getting a little 12 volt circulating fan for really hot nights. Ours is a clip-on, and we put it on a hinged counter that swings up to lock in place. May come in handy when no hookups available.
On typical warm summer nights, though, we just open the small windows, open the overhead vent, turn on the Fantastic Fan (brand name for overhead square vent fan). Most of the time, that cools things down extremely well. Quite often, one of us will even turn off the fan sometime during the night.
Most places we've been (humid or dry areas equally) may be up in the 90s or higher by day, but cool down dramatically at night. So we actually have never needed to run the AC at night even when we're plugged in.