It's going to be a damp start to Christmas Day in the Philippines as the country's weather bureau forecast the chances of heavy rains until Monday, 25 December. 

In its latest weather bulletin, the Philippine Atmospheric, Geophysical and Astronomical Services Administration said there could be peak intensities of 50 to 100 millimeters in different provinces beginning 23 December to 25 due to the combined effects of shear line and the northeast monsoon—locally known as "Amihan."

PAGASA issued a heavy rain warning from early Sunday morning until Monday that will prevail in Mainland Cagayan, Isabela, Apayao, Kalinga, and Isabela. 

It also specifically mentioned that Babuyan Islands, Quirino, Aurora, and the northern portion of Quezon province are among the areas that will experience heavy rains on Christmas Day. 

Further, the shear line will bring cloudy skies with scattered rains and thunderstorms in Mainland Cagayan, Isabela, Aurora, and northern Quezon. 

The effects of "Amihan" will prevail in the Cordillera Administrative Region and the rest of Cagayan Valley. 

Partly cloudy to cloudy skies with isolated rains or thunderstorms will be experienced in the Bicol Region, Palawan, Visayas, and Mindanao due to easterlies or localized thunderstorms. 

Under these weather conditions, PAGASA warned flash floods or landslides are possible. 

Meanwhile, isolated light rains will prevail over Metro Manila and the rest of Luzon due to the northeast monsoon. 

The weather bureau said strong winds and rough seas will be experienced over Northern Luzon and the eastern sections of Central and Southern Luzon, while the rest of Luzon and the eastern sections of the Visayas and Mindanao will have moderate to strong winds and moderate to rough seas.

The rest of the archipelago will have light to moderate winds and slight to moderate seas.