PILI, Camarines Sur — As the temperature soars, with many parts of the country including Metro Manila experiencing extremely warm weather, the term “heat index” has surfaced anew.  

In its March 6 advisory, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) warned of “danger” as the heat index rose to 45⁰ C in Dagupan City (Pangasinan) and 42⁰ in Iba (Zambales), San Jose (Occidental Mindoro) and Cuyo (Palawan). 

A temperature range of 42⁰-51⁰ is labeled as “danger” level, 52⁰ and beyond as “extreme danger,” 33⁰-41⁰ as “extreme caution,” and 27⁰-32⁰ as “caution.” Health authorities continue to warn the public to stay hydrated and to protect themselves against heat-related illnesses.

But what does “heat index” really mean?

Contrary to popular belief, the heat index is not a direct scientific measurement but a mere indicator of how the human body feels during a period of increased temperature and humidity.

“This is what the heat index aims to approximate—the level of discomfort our bodies experience due to the heat,” Dan Dominic Triumfante, a weather forecaster of Pagasa’s Southern Luzon office, told CoverStory.ph.

Triumfante explained that when the atmosphere is saturated with moisture, it becomes difficult for perspiration to evaporate, leading to heat stress. While high temperature contributes to hot weather, atmospheric moisture is the primary culprit. 

Normal phenomenon

The scorching heat noteworthy in recent days is actually a normal phenomenon due to the country’s geography, particularly its proximity to the equator. The Philippines’ numerous bodies of water also play a significant role in its humid climate. 

Face-to-face classes in many schools have been suspended to spare students the suffering brought by the heat wave. 

“My main concern about heat waves aside from the ill effects on our health is the adverse impact on MSMEs (micro, small and medium-scale enterprises). Heat wave affects our MSMEs due to reduced workforce productivity, increased operational costs, supply chain and Service disruptions,” said Natalia Dalaten, director of the Department of Trade and Industry in Pangasinan.

Rose Mary Teng-Mejia, a businesswoman and retired government worker in Dagupan, said that “it has been unusually hot, and it would be wise for us to remember to hydrate. Try to avoid strenuous activities from 10 am to 4 pm, especially for us senior citizens.”

The Philippines may experience a high heat index in the entire year, not just during the months of March, April and May. In Mindanao, the cities of General Santos, Cotabato and Zamboanga are among the areas that have been experiencing extreme heat.

Not related to El Niño

Pagasa clarified that the current heat index has no connection to El Niño, an erratic weather phenomenon characterized by long dry spells, as the country is still experiencing the tail end of the “amihan” (northwest monsoon) season. 

It has yet to declare the onset of the dry season with the sudden surge of the amihan in Northern Luzon. Another surge is projected for March 16-19, which will help determine the official start of summer, possibly by the end of March or the first week of April.

Pagasa predicted that compared to last year’s extreme heat, which was exacerbated by El Niño, this dry season will be hot but not as severe. Still, some areas, including Central Luzon, Metro Manila, and parts of Southern Luzon and Mindanao, can expect scorching weather in the coming days. – With a report from Gabriel Cardinoza in Pangasinan