Manila: Ten areas in the country will see sweltering temperatures due to dangerous index levels on Holy Monday. In its 5 a.m. forecast, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) said the following areas may have heat indices ranging from 43°C to 44°C: NAIA Pasay City, Metro Manila - 44°C; Echague, Isabela - 44°C; Sangley Point, Cavite - 44°C; Dagupan City, Pangasinan - 43°C; Tuguegarao City, Cagayan - 43°C; Subic Bay, Olongapo City - 43°C; San Ildefonso, Bulacan - 43°C; Ambulong, Tanauan, Batangas - 43°C; San Jose, Occidental Mindoro - 43°C; and Dipolog, Zamboanga del Norte - 43°C.According to Philippines News Agency, PAGASA categorizes areas with a 42°C to 51°C heat index under the danger category, while areas with 33°C to 41°C fall under the 'extreme caution' category. Heat index refers to the temperature felt by the human body when relative humidity combines with air temperature.Meanwhile, the frontal system and the easterlies will bring rains over some parts of the country. The frontal system affecting extreme Northern Luzon will cause rains across Batanes, Cagayan, and Apayao. Scattered rains and thunderstorms due to the easterlies will prevail over Zamboanga Peninsula, Basilan, Sulu, and Tawi-Tawi.Moderate to heavy rains in these areas could result in flash floods or landslides, according to PAGASA. The easterlies will also bring isolated rain showers or thunderstorms over the rest of the country. Severe thunderstorms could also result in flash floods or landslides, PAGASA warned.Meanwhile, extreme Northern Luzon will experience moderate winds and moderate coastal waters. Elsewhere, winds will be light to moderate with slight to moderate seas. No low pressure area is expected to develop or enter the Philippine Area of Responsibility, PAGASA said.