It's probably the stress of a) being in a new place and b) having to deal with hotter temperatures than I'm used to.
But I ended up with an ache behind my eyes again.
The sort of ache of either I need to drink more water or I got the wrong amount of sleep.

I didn't end up taking any meds for it though.
A bit of rest, a slight massage, and some food seem to have helped it go away. So yay!