Upper Thailand: In early March, high pressure area from China will be covered northeastern and northern parts. Cool to cold weather will persist in northeastern and northern parts include the mountainous areas. Then, in mid-March to April, Easterly and southerly winds will prevail over upper Thailand and heat low pressure cell will dominate same areas in sometimes. Cause hot weather with very hot in some areas. Maximum temperature will be 40-42°C, mainly in northern, northeastern, upper central and eastern parts. However, thundershowers and thunderstorms usually experience in upper Thailand, resulting decreasing in temperature.May is the transition period from summer to rainy season. During the first half of the month, hot weather and isolated thundershower. Then increasing in rainfall because of the southwest monsoon will prevail over Thailand, resulting in isolated heavy falls in some periods. The amount of rainfall will be slightly above normal especially in May. For the average temperature will be slightly below normal.
Southern Thailand. In March to end of April, the easterly or southerly winds prevail over southern Thailand. Cause widely scattered to scattered thundershowers and hot weather in some days. Waves height in the Gulf of Thailand and the Andaman Sea will be 1 meters. Then, the southwest monsoon will prevail over the Andaman Sea and southern Thailand. Resulting increasing in rainfall especially in the west coast with isolated heavy falls. The amount of rainfall will be slightly above normal and the average temperature will be will be slightly below normal.