‘Tis the season…for low humidity in may parts of the country. As soon as the windows are shut and the heaters turn on, the humidity will drop. If you have acoustic guitars, hollowbodies, or semi-hollowbodies, make sure the humidity stays at a comfortable level or you could be facing cracks in the instruments. And any guitar, hollow or solidbody, can have problems with the neck warping if the humidity changes significantly.
To prevent these problems, get a hygrometer (humidity meter) and keep it with your instruments. Basically, guitars are comfortable in the same range as people are — 40-60% humidity. If the humidity falls below 40% or so, you need to get some water in the air or into your guitar’s case.
But be careful of going too far – more than 60% humidity may result in the guitar swelling, which can in turn result in busted glue seams or wood cracks.