Thailand experienced a rare 'zero shadow day' as the sun rose directly overhead in the country today.

Footage shows the sunlight appearing to cast no shadows during a short period as the phenomenon was observed in Bangkok on April 27.

The National Astronomical Research Institute of Thailand (NARIT) said the sun was at its zenith position, when its rays strike exactly vertically relative to an object on the ground.

All regions between the tropics of Cancer and Capricorn experience 'zero shadow day' twice a year. However, it only lasts for a few minutes before the Earth and Sun shift out of sync.

The second 'no shadow day' window will occur again in Thailand between July to September, with Bangkok expected to observe it late noon on August 16.

NARIT also clarified that 'zero shadow day' was not necessarily the hottest day of the year, as the temperature depends on other factors like rainfall, cloud cover, humidity, and accumulated heat.