The easterlies remain the dominant weather system that may bring humid weather over the country and scattered rain showers over Palawan and some parts of northern Mindanao.
In its weather bulletin issued on Sunday, May 16, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) said scattered rain showers and thunderstorms may affect Bukidnon, Camiguin, Misamis Occidental, Misamis Oriental, Lanao del Norte, Zamboanga Sibugay, Zamboanga del Norte, Zamboanga del Sur, and Palawan.
Those in these areas were advised to take extra precautions due to possible flash floods or landslides during moderate to at times heavy rainfall.
Meanwhile, the rest of the country will remain hot and humid but with chances of isolated rain showers and thunderstorms most likely in the afternoon or evening.
PAGASA also advised the public to remain vigilant due to potential flash floods or landslides during severe thunderstorms.
Based on its extended weather outlook for key areas from May 17 to 20, PAGASA said that maximum air temperatures may reach 35-36 degrees Celsius (℃) in Metro Manila, 38℃-39℃ in Tuguegarao City, 27℃-28℃ in Baguio City, 32℃ in Tagaytay City, 32℃ in Puerto Princesa City, 32℃-33℃ in Metro Cebu, 32℃ in Metro Davao, and 33℃-35℃ in Zamboanga City.
The highest recorded air temperature in the Philippines was 42.2 degrees Celsius in Tuguegarao, Cagayan on May 11, 1969.
Meanwhile, the highest recorded air temperature in Metro Manila was 38.5 degrees Celsius on May 14, 1987.
Air temperature is different from heat index as the latter is the measurement of how hot it feels when relative humidity is factored in with the actual air temperature.
The heat index is at least 3℃ to 4℃ higher than the actual air temperature.
The highest heat index so far in 2021 was recorded in Dagupan City, Pangasinan on May 14 at 53℃.