The Meteorological Department says this summer, which officially began on Wednesday, will see temperatures rise to a blistering 45C on some days, with daytime averages hovering around 36C.
The warmer temperatures are being brought on by strong sunlight over the upper regions of the country, which are carried over to other regions by a southerly wind that prevails during the summer season.
As a result, the North and the Northeast could expect to see cooler temperatures until mid-March, the department said in an announcement.
This year's "hot" season will end in mid-May, it noted.
This summer, the average temperature is expected to hover between 36-37C. Last year, the average temperature was 35.8C.
Somkhuan Tonjan, director of the forecast sub-division, said March and April would be the hottest months, with highs reaching 43-44C.
However, some areas could see the mercury rise to 45C, higher than the record of 44.6C registered in Mae Hong Son in 2016 and in Tak province last year.
The El Nino-Southern Oscillation will continue to have an impact on the weather throughout the summer, though it will begin to subside as the year progresses.
This would result in dry weather at the start of the year, he said, noting rainfall could be 30% below normal, and its distribution would not be favourable to agriculture.
This would result in drought outside irrigated zones. There may be shortages of water, both for domestic use and the agricultural sector, Mr Somkhuan warned.
In stark contrast, the temperature dropped to 3C at the top of Thailand's highest mountain, Doi Inthanon, in Chiang Mai, yesterday morning, with frost coating the leaves of plants. In the lowland areas of Chiang Mai, temperatures ranged between 14-16C.
The cool weather and frost, or moei khab, drew many tourists to the Kiew Mae Pan viewpoint on Doi Inthanon.