Your guitar is made of thin wood which is easily affected by temperature and humidity. This combination is the most important single part of your guitar’s surroundings. Martin keeps the factory at a constant 45-55 percent humidity and 72-77 degrees Fahrenheit. If either humidity or temperature get far away from these factory conditions, your guitar is in danger. A rapid change in temperature or exposure to cold can cause small cracks in the finish. These are lacquer checks. We recommend the use of a hygrometer/ thermometer to measure the relative humidity and temperature surrounding your guitar.