Typhoon Mangkhut's ferocity is being compared to that a Category 5 Atlantic Hurricane.
Philippines officials have ordered evacuations and closed schools and offices as Typhoon Mangkhut neared, carrying sustained winds of more than 200km/h (125mph).
The charity estimates three million people in the country live in the direct path of Mangkhut.
The typhoon, expected to be closer to south China by the weekend, will bring heavy rains and storm surges on its trail.
While Mangkhut is now stronger than Hato -- also known as Tropical Storm Isang -- or Haima it is likely to decrease in strength as it nears southern China, particularly if it crosses land over northern Luzon, which will slow the storm, according to Guy, the meteorologist.
Weather specialist Aldczar Aurelio of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) said Tropical Depression "Neneng" brought light to moderate rains over the Batanes and Calayan group of islands on Monday as it formed 22 kilometers north of capital town of Basco.
It said that Mangkhut packed maximum sustained winds of up to 185 kph near the center and gustiness of up to 220 kph.
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Officials of the state weather bureau - Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) - said in a livestreamed press conference on September 12 that the typhoon is seen to reach a peak intensity of 220 to 270 kilometers per hour (kph).
In 2016, a super typhoon lashed southern parts of Cagayan, destroying tens of thousands of houses. Mangkhut is blowing from the Pacific and forecast to directly slam the province's northeastern coastal and island municipalities, Mamba said.
"I'm stressing that this one is very different".
The typhoon is arriving at the start of the rice and corn harvest season in Cagayan, a major agricultural producer, and farmers were scrambling to save what they could of their crops, Mamba said.
A missile test aboard a navy ship to be attended by president Rodrigo Duterte off northern Bataan province was cancelled due to the approaching typhoon.
Once the Typhoon enters the vicinity of Philippines on Wednesday afternoon, "Mangkhut" will be named as "Ompong" locally.
Mangkhut is expected to be as strong as Haiyan - a super typhoon that killed more than 6,200 people in the Philippines in 2013.