The Noon Without a Shadow: Thailand Enters First ‘Zenith Sun’ Cycle of 2026
Thailand begins its first "Sun Overhead" cycle of the year in Yala, creating a rare shadowless effect—though experts warn it may not be the hottest day
- Thailand is experiencing its first "Zenith Sun" cycle of 2026, an astronomical event where the sun is directly overhead at noon, causing a temporary "shadowless" effect.
- The event began on April 4 in the southern province of Yala and will progressively move northward across the country, concluding on May 22 in Chiang Rai.
- This phenomenon occurs twice annually in Thailand because the country is situated within the Earth's tropics, the only region where the sun can be at a 90-degree angle overhead.
- Despite the sun's maximum intensity during the event, experts note that this day is not necessarily the hottest of the year, as temperature is influenced by other factors like cloud cover and monsoons.
Thailand begins its first "Sun Overhead" cycle of the year in Yala, creating a rare shadowless effect—though experts warn it may not be the hottest day.
Residents across Thailand’s 77 provinces are set to experience a rare astronomical curiosity over the coming weeks as the sun reaches its zenith directly overhead, momentarily rendering shadows invisible.
The National Astronomical Research Institute of Thailand (NARIT) has released a comprehensive timeline for the first of the year’s two "Sun Overhead" events. The cycle commenced today, 4 April 2026, in the southernmost district of Betong, Yala, at precisely 12:19 PM.
During this window, anyone standing outdoors will notice that their shadow—and those of vertical objects like lamp posts—falls directly beneath them, creating a "shadowless" illusion.
A Northward Journey
According to Suparerk Karuehanon, assistant director of NARIT, the phenomenon does not occur simultaneously across the country.
Because of the Earth’s curvature, the sun’s 90-degree vertical alignment will gradually "march" northwards through April and May.
The Starting Point: Betong, Yala (4 April at 12:19 PM).
The Final Destination: Mae Sai, Chiang Rai (22 May at 12:17 PM).
A second cycle is expected later in the year, between July and September, as the sun’s relative position moves back from the north towards the south.
Maximum Energy, Not Always Maximum Heat
While the sun sitting directly overhead allows the Earth to receive the maximum possible intensity of solar energy, NARIT has moved to dispel the myth that this date will automatically be the hottest of the year.
"The temperature on any given day is dictated by a complex variety of factors," NARIT explained. "Accumulated atmospheric heat, cloud cover, seasonal monsoons, and rainfall all play a significant role. Consequently, the 'Shadowless Day' in your province may not necessarily coincide with the peak temperature recorded this summer."
The Science of the Tropics
The event is a quirk of geography. Because the Earth’s axis is tilted at approximately 23.5 degrees, the sun can only reach a true vertical zenith in the "Tropics"—the region between the Tropic of Cancer (23.5°N) and the Tropic of Capricorn (23.5°S).
As Thailand sits comfortably within this tropical belt (latitudes 5°N to 20°N), it is uniquely positioned to witness this alignment twice annually.
The specific timing for each province depends entirely on its latitude, meaning a resident in Bangkok will experience the "Shadowless Noon" on a different date to a resident in Chiang Mai.
For those curious to see the exact minute their shadow will disappear, NARIT has published a full 77-province schedule on their official website.
