I bought a Rainsong guitar (carbon fibre) that is inert to such issues. It spent most of its time in The UK but I took it with me every year to The French Alps and also a couple of times to Alberta, Canada.

Here in The UK, it really isn't an issue, although playing in a marquee recently with hot humid air, my (normal) guitar was having problems staying in tune and a bit of fret buzz... Back to normal the next day.

We stay with friends in Canmore when in Canada and they bought their son a guitar back when they lived in Australia (Queensland, hot humid etc.). It split like a log under an axe... Really low humidity.

My niece plays cello and is based in Singapore, but she also keeps cellos in Australia, The USA and The UK. The Singapore instrument isn't allowed to travel, no matter which orchestra asks for her...

I bought a Terry Pack guitar recently and was bemused to see a hygrometer in the case. A nice touch, but for The UK market, (they are based in Blackpool) a little over the top.