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Dangerous heat index: How harmful and how to mitigate its health effects?

Several areas in the country have been experiencing a heat index at a danger level in the past week amid the effects of the El Niño phenomenon, according to state weather bureau PAGASA.

PAGASA said the heat index in the country may get worse this April.

But how serious are the possible effects of high heat index on the health of the exposed population and how to mitigate them?

Heat index

According to PAGASA, the heat felt by the human body or the “apparent temperature” is not accurately measured using only the air temperature. This hot feeling is more correctly estimated with humidity.

Heat index is the measure of the temperature that a person feels, which is computed considering air temperature and humidity, said PAGASA.

There are four classifications of heat index based on the possible effects of the temperature to people:

  • Caution - from 27 to 32 degrees Celsius
  • Extreme Caution - from 33 °C to 41°C
  • Danger - from 42°C to 51°C
  • Extreme Danger - from 52°C and beyond 


In the extreme danger level of heat index, heat stroke is imminent, according to PAGASA.

For the danger level, heat cramps and heat exhaustion are likely, and heat stroke is also probable with continued exposure.

In the extreme caution level, heat cramps and heat exhaustion are possible and continuing activity could lead to heat stroke.

Meanwhile, with the caution level, fatigue is possible with prolonged exposure and activity and continuing activity could lead to heat cramps.

Among the causes of health-related illnesses are prolonged exposure to hot temperatures, exhausting activities in warm weather, old or young age, weak immune system, high humidity, obesity, and chronic alcoholism.

The symptoms are sweating heavily, exhaustion or fatigue, dizziness or lightheadedness, blacking out or feeling dizzy when standing, weak but fast pulse, nausea, and vomiting.


As Filipinos currently bear the brunt of the El Niño phenomenon, the Department of Health (DOH) gave reminders on how to avoid heat stroke, especially in areas where there is a dangerous level of heat index.

DOH Undersecretary Eric Tayag said that while everyone is at risk during this time of extreme heat, the elderly, those who work directly under the sun, and even those who stay in houses where there is not much ventilation or insulation may be more vulnerable to heat stroke. 

He thus primarily advised to keep drinking lots of water to prevent dehydration. 

“Importante na minomotor natin ang ating nararamdaman. Lalo na sa pag-inom ng tubig, kinakailangan sapat o dagdagan pa kasi ang dehydration ang kalaban natin diyan,” the DOH spokesperson said in an interview with Balitanghali. 

(It’s important that we monitor our condition. It’s especially necessary to drink enough water or even more because dehydration is our main enemy here.) 

The DOH likewise advised the public to refrain from leaving the house at noontime and to do so only in the morning or in the afternoon.

People should also wear light and loose clothing to keep the body cool.

Emergency response

Tayag said a person may suffer from heat stroke if his/her body temperature spikes to 40 degree Celsius or higher. 

He also warned that heat stroke is deadly if the victim does not receive immediate treatment or is not brought to the nearest hospital. 

“Mapapansin din naman na talagang kayo’y malalagay na sa panganib kasi namumula na ang balat ninyo, nababawasan na ang pawis, at may hinihimatay pa o kaya nagkakaron ng muscle cramps. ‘Yan ay isang emergency kapag heat stroke,” Tayag explained.

(You will notice that your life’s in danger when your skin gets red, your sweat is reduced, or when you faint or get muscle cramps. That's an emergency in case of heat stroke.) 

In its health advisory, DOH reminded the following first-aid tips should a person suffer from heat stroke: 

  • transfer the person to a cooler or shady area
  • remove clothes that could add up to body heat
  • apply cold compress on the underarm, groin, neck, and back
  • soak the person in cold water, if possible

Dangerous level

PAGASA said the following areas are expected to experience a “danger” level of heat index on Monday:

  • Aparri, Cagayan: 43 degrees Celsius
  • CBSUA in Pili, Camarines Sur: 42°C
  • Catarman, Northern Samar: 43°C
  • Zamboanga City, Zamboanga del Sur: 42°C

Due to the hot weather, classes have been suspended in the following areas:

  • Bacolod City: no face-to-face classes, preschool to senior high school, public and private
  • Iloilo City: no face-to-face classes, preschool to senior high school, public and private, until April 2
  • Roxas, Capiz: no face-to-face classes, preschool to senior high school, public and private
  • Kabankalan, Negros Occidental: no classes in all levels, public and private
  • E.B. Magalona, Negros Occidental: no face-to-face classes in all levels, public and private, until April 2
  • Tantangan, South Cotabato: half-day classes for April 1 to 15 in all levels, public and private

PAGASA declared the start of the El Niño phenomenon on July 4 last year.

The El Niño phenomenon is characterized by the abnormal warming of sea surface temperature in the central and eastern equatorial Pacific Ocean leading to below normal rainfall.—AOL, GMA Integrated News