The storm is generating powerful winds of at least tropical storm force over a wide swath that also includes parts of China and Japan.
Hinnamnor comes about a month after record-setting rainfall brought deadly flooding to Seoul.
The terms typhoon, hurricane and cyclone all refer to tropical cyclones; the term that is applied to a given storm depends on where it originates. Typhoons develop in the northwestern Pacific and usually affect Asia. Hurricanes form in the North Atlantic, the northeastern Pacific, the Caribbean Sea or the Gulf of Mexico.
In the Atlantic, major hurricanes are defined as tropical cyclones with maximum sustained winds of 111 m.p.h. or higher and are classed as either Category 3, 4 and 5 storms. But in the Asia Pacific region, there are variations in how individual countries grade typhoons.