Sun at zenith dazzles across Thailand without creating hottest day

Today, a solar phenomenon graced all 77 provinces of Thailand, with a sun at zenith event that stretched from the southernmost district of Betong to Mae Sai in Chiang Rai. There’s a common misconception that such an event marks the hottest day of the year, but this is not necessarily the case.

The National Astronomical Research Institute of Thailand (NARIT) shared a post on Facebook detailing the timeline for when the sun would be at its zenith in each of the 77 provinces in 2024. The event, which began on April 4, in Betong, Yala, will culminate on May 22, in Mae Sai, Chiang Rai.

During this period, objects will appear to cast no shadow at noon because their shadows will fall directly underneath them. However, the assumption that these will be the hottest days is influenced by various factors and is not guaranteed.

From April to May, the sun orbits to a position directly overhead in Thailand for the first time of the year, starting from the south in Yala today, April 4, at approximately 12.19pm. As the days progress, the sun continues its northward trajectory, eventually reaching Chiang Rai on May 22 at around 12.17pm.

Observing objects around the local noon during this period will reveal an almost shadowless sight, as shadows align perfectly with the base of the objects due to the sun’s overhead position.

Despite the intense solar energy received when the sun is at its zenith, whether temperatures will soar to their peak depends on a variety of factors, including rainfall, cloud cover, monsoonal influences, and accumulated heat, suggesting that these may not necessarily be the warmest days of the year.

Thailand’s geographical position, between 5 and 20 degrees north latitude in the tropical zone, allows for the sun to pass near the zenith twice each year—once between April and May, and again between July and September, reported Sanook.

The exact dates and times of this phenomenon vary by location, which means that each province in Thailand experiences the sun at its zenith at different moments.