This year is expected to be cooler than 2016, according to the Thai Meteorological Department.
Wanchai Sakudomchai, the department's director general, said yesterday temperatures this year, with the highest estimated at between 42-43C, are expected to be lower than they were in 2016.
The onset of the summer season started last Friday and will last until mid-May, he said.
Mr Wanchai said the department decided to announce the beginning of summer after it observed a change in wind patterns and soaring temperatures during the day time.
The northeastern monsoon has faded away while the southeastern monsoon has prevailed over Thailand, signifying that the summer season has begun, Mr Wanchai added.
Last year, Mae Hong Son saw the highest temperature ever recorded in the country of 44.6C. This year in Bangkok, the highest temperature is forecast to be around 40C, he said.
The department predicts the North and the Northeast will experience some of the hottest weather this summer, he added.
Meanwhile, Chayapon Thitisak, deputy permanent secretary for the Interior Ministry, said that the Interior Minister has ordered local officials in northern provinces, which have been affected by haze pollution, to set up provincial command units to bring air pollution in these provinces under control.
The levels of harmful air particles in the northern provinces including Chiang Mai, Mae Hong Son and Lampang have exceeded the safety limit, thereby posing health risks, he said.
The level of harmful particles in tambon Bandong, Mae Mo district was 168 microgrammes per cubic metres (u/cg) and it was 144u/cg in tambon Phra Baht, Muang district, which exceeds the safety limit of 120 u/cg.