Book excerpt: This study is one of a revised series of publications dealing with the climate of Southeast Asia on a monthly basis. For the purpose of this study, Southeast Asia is defined as North Vietnam, Republic of Vietnam, Laos, Cambodia and Thailand. The format has been organized in an effort to provide ready reference material to meet a variety of requirements for different users; however, information contained in this publication is based on climatic averages and should not be construed as a forecast. Conclusions drawn from isoline charts occasionally appear in conflict with, or unsubstantiated by, reported station values. This situation arises frequently in those areas lacking adequate station data, where isoline analyses were based wholly or in part on information other than actual station values. Further interpretation of data contained in this study should be made by a qualified Meteorologist. (Author).