BANGKOK: Thailand will once again experience the “sun overhead” phenomenon in 2026, with the National Astronomical Research Institute of Thailand (Narit) releasing a full timeline covering all 77 provinces.
The phenomenon occurs twice each year, when the sun passes directly overhead at midday, causing objects in open areas to appear as though they cast no shadow. This happens because shadows fall directly beneath the object.
For the first occurrence in 2026, the event will begin in the southernmost part of the country at Betong district in Yala province on April 4 at approximately 12:19pm.
The sun will then gradually shift northward, passing over different regions of Thailand in sequence, before reaching the northernmost point at Mae Sai district in Chiang Rai province on May 22 at around 12:17pm.
A second cycle will occur later in the year, with the sun moving from north to south, typically between July and September.
Despite receiving maximum solar energy when the sun is directly overhead, this does not necessarily correspond to the hottest day of the year. Temperatures are influenced by a range of additional factors, including cloud cover, rainfall, monsoon patterns and accumulated heat.
The phenomenon is linked to the Earth’s axial tilt of approximately 23.5 degrees, which causes the angle of sunlight to vary across different regions throughout the year.
As a result, the sun can only appear directly overhead within tropical regions — between the Tropic of Cancer (23.5 degrees north latitude) and the Tropic of Capricorn (23.5 degrees south latitude).
Thailand lies within this zone, roughly between 5 and 20 degrees north latitude, allowing the sun to pass close to the zenith twice annually.
Because each location has a slightly different latitude, the exact date and time of the “no shadow” moment varies across provinces.
Narit has published a full schedule detailing when the phenomenon will occur in each of Thailand’s 77 provinces, enabling the public to track and observe the event locally. - The Nation/ANN
