Nanmadol made landfall just before daybreak in Taitung county in the remote southeast and headed toward heavily populated coastal areas on the west coast. It had winds of 68 mph (108 kph), down from earlier peaks almost twice that high.
It hit Taiwan after claiming at least 12 lives in the Philippines, and leaving another nine people missing. It was expected to pass about 130 miles (200 kilometers) south of Taiwan's capital, Taipei, before heading for the Taiwan Strait and the eastern coast of China.
As of 10 a.m. (0200 GMT), many domestic flights had been canceled, and officials with Taiwan's high speed rail network, which serves heavily populated areas along the west coast, were weighing a suspension of services. The storm had dumped almost 20 inches (half a meter) of rain in the mountainous south, where vulnerability to catastrophic landslides led to the evacuation of some 8,000 people.
According to the website of Taipei's main international airport, almost all overseas flights were operating normally.
With its enormous cloud band, the slow moving typhoon drenched the northern part of the Philippines with rain for days before pummeling the area with fierce winds, setting off landslides and floods and knocking down walls, the cause of the majority of casualties in that country, said Benito Ramos, who heads the Office of Civil Defense.
In Taiwan, the area most severely affected by the early phase of the storm was Pingtung county in the southwest, where civil defense crews used small boats to rescue people from rural communities inundated by flash flooding.
Pingtung is just to the south of the mountainous regions where more than 500 people died two years ago in mudslides spawned by torrential rains associated with Typhoon Morakot, the most devastating storm to hit the island in half a century.
A slow government response to that catastrophe prompted a fusillade of criticism aimed at President Ma Ying-jeou, who is up for re-election this January.
In the immediate wake of Morakot, Ma announced that he was reorienting the major mission of the island's armed forces away from defending against a possible Chinese invasion – the two sides split amid civil war in 1949 – and toward disaster relief. That was evident over the course of the weekend, as the military dispatched troops and rescue equipment to vulnerable areas, unlike during Morakot.