It's COLD out there
Protecting Your Guitar from Unusually Low Temperatures
Unusually cold climatic conditions can pose dangers to your guitar, but is mainly detrimental to finish. “Finish checking” (small cracks in the finish) is common where temperatures drop below the freezing point. This can result from having your guitar outside in below freezing weather, then immediately upon entering a warm room, opening the case to remove your guitar (or vice versa).
If in spite of your best efforts the finish does become “checked”, it is worth noting that this only affets the appearance of the guitar, and will not affect its lifespan, playability, or sound. Most people learn to live with the “checks”, as correction of this problem would require a costly finishing repair not covered by your warranty. Also keep in mind, re-spraying the top can alter the tone, especially in the case of an older instrument.
The above problems can be avoided by taking a few simple precautions:
Keep your guitar in a cool place at 5°C to 10°C (42°F to 50°F) for an hour or so before going outside. The same rule applies when bringing your guitar in from the cold. Allow it to warm up gradually with the case closed for at least one hour. Ideally, you should try and avoid exposing your guitar to extremely frigid temperatures altogether.
Never leave your guitar hanging on the wall in winter, as heat will rise. While floor temperatures may be 18°C, five feet above the floor it may be 22°C, and at eight feet 27°C! At these temperatures, the relative humidity tends to become relatively low, giving rise to the problems associated with excessive winter weather (see section 4 below).
The humidity in your home during winter should be kept at approximately 45% relative to 22°C for the safety of your guitar. If it dips too much lower, problems may arise. Try to keep your guitar in a cooler place and in the case when possible. Use a Dampit® or a similar device that retains water, but make sure to check it frequently, as these units contain only a small amount of water and can completely dry out within the first eight hours.