Typhoon Mangkhut, with winds of 255 km/h (160 mph), is due to reach land on the northern tip of the main island of Luzon by the weekend.
Schools and offices are being shut and farmers are hurrying to save crops.
Ten million people are in the way of the storm, along with millions more in coastal areas of southern China.
The Philippines is buffeted by about 20 typhoons and storms a year. Forecasters say Mangkhut is the strongest so far in 2018 – 900 km in diameter, with sustained winds of 205 km/h, equivalent to a Category 5 Hurricane and stronger than Hurricane Florence which is currently lashing the US East Coast.
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Authorities in the Philippines say they expect storm surges of up to 7 m (23 feet) and are cautioning that heavy rains could cause landslides and flash floods.
Image credit: EPA