The prevalence of warm and humid weather conditions has continued to push the heat index values above 40 degrees Celsius (°C) in 10 areas in Luzon on Wednesday, May 19.
The heat index is the measurement of how hot it feels when relative humidity is factored in with the actual air temperature.

Based on the monitoring of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the following areas recorded the top 10 heat index values on Wednesday.
Dagupan City (47°C, 11 a.m.)
Aparri, Cagayan (46℃, 11 a.m.)
Ambulong, Batangas (43℃, 2 p.m.)
Laoag, Ilocos Norte (43℃, 2 p.m.)
Sangley Point, Cavite (43℃, 11 a.m.)
Tuguegarao City, Cagayan (43℃, 2 p.m.)
Clark Airport, Pampanga (42℃, 2 p.m.)
San Jose, Occidental Mindoro (42℃, 11 a.m.)
Masbate City, Masbate (41℃, 12 p.m.)
Ninoy Aquino International Airport, Pasay City (41℃, 11 a.m.)
A heat index above 40℃ is considered "dangerous" due to the high likelihood of heat cramps and heat exhaustion.
So far, the highest heat index in 2021 was registered in Dagupan City, Pangasinan at 53℃ on May 14.
PAGASA said the easterly winds that bring warm and humid weather conditions across most parts of the country will continue to affect Luzon, except Palawan, on Thursday, May 20.
Meanwhile, the intertropical convergence zone (ITCZ) may bring scattered rain showers and thunderstorms over Palawan, Visayas, and Mindanao.
ITCZ is a region where trade winds from the northern and southern hemispheres converge, which is characterized by frequent and often severe thunderstorms.
PAGASA warned against possible flash floods or landslides due to moderate to at times heavy rains.