Source: The Library Of Congress Country Studies
Thailand has a tropical monsoon climate; temperatures normally range from an average annual high of 38° C to a low of 19° C. Southwest monsoons that arrive between May and July (except in the South) signal the advent of the rainy season (ridu fon), which lasts into October. November and December mark the onset of the dry season. Temperatures begin to climb in January, and a hot sun parches the landscape. The dry season is shortest in the South because of the proximity of the sea to all parts of the Malay Peninsula. With only minor exceptions, every area of the country receives adequate rainfall, but the duration of the rainy season and the amount of rain vary substantially from region to region and with altitude. The Northeast experiences a long dry season, and its red, porous (laterite) soils retain water poorly, which limits their agricultural potential.
Data as of 1987