Tomorrow will be the longest day of the year in Thailand, says NARIT

Tomorrow (June 21) will be the longest day of the year in Thailand, due to the phenomenon of the summer solstice, according to the National Astronomical Research Institute of Thailand (NARIT).

The institute explained that the summer solstice occurs when the day is the longest and the night the shortest of the year, as the sun reaches its "stop point" or "northernmost point" along its apparent path across the sky. This phenomenon happens at the same time every year, beginning in March.

The sun appears to move approximately one degree northward each day, reaching its northernmost point on June 21. As a result, on this day, the sun rises from the northeastern horizon and sets at the northwestern horizon, making it the longest day of the year in Thailand."The sun will rise at approximately 5.51am and set at around 6.47pm, giving a total of about 12 hours and 56 minutes of daylight (in Bangkok time)," NARIT said.

The summer solstice also marks the beginning of summer in countries of the Northern Hemisphere, such as China, Japan, the United States, and Europe. In contrast, countries in the Southern Hemisphere, like Chile, Australia, and New Zealand, will begin to experience winter at the same time.NARIT further explained that the Earth's seasons are caused by the tilt of the Earth's axis, which is tilted at an angle of approximately 23.5 degrees relative to the plane of its orbit around the sun.

This tilt results in varying amounts of solar energy reaching different parts of the Earth, leading to differences in temperature and the length of day and night. Thus, in summer, the days are longer than the nights, with the sun rising early and setting late. In winter, the opposite occurs: nights are longer, and the sun rises later and sets earlier.

NARIT also mentioned that the next solar-related event is the autumnal equinox, which will occur on September 23 this year. 

On this day, the sun will rise directly in the east and set directly in the west, resulting in equal lengths of day and night. This marks the transition between seasons, with countries in the Northern Hemisphere entering autumn, while those in the Southern Hemisphere begin spring.

This phenomenon, which occurs annually, is significant both scientifically and culturally, NARIT concluded.

(2025/06/20-00:00)