Hong Kong lies directly in the path of the storm.
Schools and businesses shut down as the city braced itself for the arrival of the typhoon on Tuesday.
The typhoon is thought to be particularly threatening because it has a "double eye".
Strongest
That means that the winds will be even stronger than normal, and twisting in loads of directions.
Hong Kong is struck by six or seven typhoons each year.
But this one is already being seen as the strongest of 2003.
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