Twelve areas in the country on Friday are expected to experience a heat index classified as dangerous, according to the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA).

Two provinces are forecast to have the highest heat index, with their temperatures hitting 44°C, namely Ambulong in Tanauan, Batangas, and Aborlan in Palawan.

Meanwhile, a heat index of 43°C is projected to be felt in six areas: Dagupan City in Pangasinan, Sangley Point in Cavite, Puerto Princesa City in Palawan, Roxas City in Capiz, and Iloilo, namely Iloilo City and the town of Dumangas.

On the other hand, four areas in the country may have their temperatures peaking at 42°C: Bacnotan in La Union, Tuguegarao City in Cagayan, Central Bicol State University of Agriculture in Pili, Camarines Sur, and Dipolog in Zamboanga del Norte.

Baguio City and Benguet State University in La Trinidad remain to have the lowest expected heat index of 28°C.

PAGASA defines the heat index as the human discomfort index that gives the "apparent" temperature, or what humans perceive or feel as the temperature affecting their body.

The effect-based danger classification ranges from 42°C to 51°C, and its effects on the body are that heat cramps and exhaustion are likely, and heat stroke is probable with continued exposure.

Taking preventive measures such as limiting time spent outdoors, drinking plenty of water, and wearing protective and comfortable clothing outdoors is strongly advised by the government to the public to avoid heat-related illnesses.