The Meteorological Department forecast is for extremely hot weather from Monday to Sunday, with temperatures likely to peak in the North at 43 degrees Celsius on Monday.
The heat is the result of a low pressure zone expected to remain over the North, Northeast, Central and East regions from April 22-28. The weather is expected to be very hot and overcast.
Temperatures could reach 43°C in the North, 42 degrees in the Central Plains, 41 degrees in Greater Bangkok, the Northeast and the East and 40 degrees in the South on Monday, the weather office said.
It advised people to refrain from extended outdoor activities if possible.
Thunderstorms are possible in some areas, brought by southeasterly and southerly winds. Rain was expected in the lower South due to westerly and northwesterly winds over the Andaman Sea and the South, the department said.