The latest forecast from the Philippine Atmospheric, Geophysical, and Astronomical Services Administration shows that some areas in Cagayan Valley will experience a heat index of 42 degrees Celsius on Wednesday.

Based on their report, Tuguegarao City and Appari town heat indexes are estimated to slightly decrease on Thursday at 40 degrees Celsius and 39 degrees Celsius, respectively.

Meanwhile, other areas in the country that were projected to have experienced a 42-degree Celsius heat index in the past few days were Bacnotan in La Union, Calapan in Oriental Mindoro, Coron in Palawan, and Cotabato City in Maguindanao.

The heat index, as defined by PAGASA, is the measure of the contribution that high humidity makes to abnormally high temperatures by reducing the body's ability to cool itself.

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

Thus, PAGASA urged the public to take preventive measures to avoid the heat having a detrimental effect on one’s health, such as limiting time spent outdoors, drinking plenty of water, avoiding tea, coffee, soda, and liquor, and wearing hats, sleeved clothing outdoors, and umbrella.