Consequences of extremely dry conditions.

Fingerboards will tend to shrink causing frets to extend beyond the edge of the fingerboard. These fret ends are often sharp and may need to be filed. Since the soundboard and back are glued to the sides, they will stretch being held in place by the guitar’s structure -- this is what causes these larger components of the guitar to crack. You may also see the smaller joints appear to open up in areas of purfling or even in the rosette. Other components like bridges are rarely hurt by dry conditions, but bridges can lift as a result of extreme dryness.

Since wood is a hydroscopic material which releases and absorbs water slowly, you may be safe for a shot periods of time in dry conditions, but eventually as your guitar dries out, you will eventually see these symptoms appear. Dry to avoid extended periods of dry conditions by using a household humidifier or keeping your acoustic guitar in a Humicase.