Desert is ruining my guitars grrrrr

Ok, here's what's going on.
I live in the Mojave Desert (yay me!!) and its causing me issues with my guitars.

I've a warped neck on one, and my taylor seems to be going the same way. To keep the trailer cool, we have a very efficient swamp cooler - the down side of that is the humidity in the trailer is quite high. My guitars are stored in their cases when not in use, and I have the silica gel packets in all cases as a short term fix.

How can I stop the humidity/temperature causing any further problems with my guitars?

Wurzel