Climatic conditions in Thailand and their effect on museum environments are described. The climate is tropical, with relative humidity in the coastal regions averaging around 80 percent and temperature averaging around 27 degrees C. Most national museums are modified historic buildings, and thus are subject to a variety of problems, such as leakage of rain water. Energy policies preclude use of air conditioning systems in most museums, with the exception of two galleries in the Bangkok National Museum and National Art Gallery. However, because the systems only operate seven hours a day, temperature and relative humidity fluctuate dramatically in these galleries. Freestanding dehumidifiers are used in some rooms, and silica gel is used to control humidity inside display cases and storage cabinets.