A woman uses a fan as she tries to deal with the heat in Navotas City on April 22, 2024. Jonathan Cellona, ABS-CBN News/fileMANILA — Despite several weeks of scorching temperatures that would convince any ordinary citizen into concluding that what is happening is a heat wave, state weather bureau PAGASA says it still isn’t so.

Filipinos are in experiencing high heat indices, some of which pose dangers to human health. 

On Friday, close to 40 areas in different parts of the country logged heat indices of over 42 degrees which is categorized as dangerous.

PAGASA climatologist Dr. John Manalo said the possibility of more areas hitting heat indices of 42 degrees and higher in the next couple of weeks is highly likely. 

It is also important to understand that an area’s topography also is among the reason behind a higher heat index.

'So hot you can't breathe': Extreme heat hits the Philippines

“Low-lying areas like Tuguegarao, Dagupan, Aparri and some parts of Eastern Samar and Mindanao experience a higher heat index. Aside from low elevation, their distance to the coast, rivers and other bodies of water is also a factor,” he explained in Filipino.

The heat index takes into consideration an area's relative humidity.

“The higher the relative humidity, the higher the heat index.”

But he clarified that a heat wave is still not present.

“It’s very rare, but we still don’t omit the possibility that it can happen. If it does happen, it will only be in a specific area and not for the entire country.”

According to the World Meteorological Organization, a heat wave is defined as a “period where local excess heat accumulates over a sequence of unusually hot days and nights.” 

Heat waves amplify many risks especially to health and may cause death and affect agriculture through droughts, wildfires and other hazards. 

44-degree scorcher threatens Metro Manila 

Manalo said this means certain parameters have to be met including the mercury reaching temperatures 5 degrees Celsius higher than an area’s climatological temperature. 

Simply put, if Metro Manila’s average maximum temperature is 34 degrees Celsius, it would have to log a temperature of 39 degrees or higher for the next 5 days, for the extreme heat to be considered a heat wave. 

But heat wave or not, it remains clear that prolonged exposure to sweltering heat is a health threat. This is why experts keep reminding the public to cool down and hydrate frequently.