The microclimatic patterns in a large, metropolitan center situated in a warm and humid climatic zone have been investigated in relation to various forms of land use. The survey was conducted in Houston, Texas in the fall and summer of two consecutive years. Information on temperature and humidity obtained during the survey along with demographic and land-use data were mapped utilizing synographic computer techniques to detect anthropogenic changes in the microclimatic characteristics of the area. Results indicate that a thermal anomaly of man-made origin in this city does exist in spite of the anticipated advantages of its coastal location. Quantitative information derived from the study can be of practical value for urban development planning in areas of hot and humid climates.