Widespread flight cancellations were set to bring chaos to Hong Kong's busy international airport as Typhoon Hato churns towards the city on Tuesday.
The weather observatory said the storm would pass within 100 kilometres of Hong Kong on Wednesday morning, "posing considerable threat" to the territory.
It warned of strong winds, rough seas and possible flooding due to heavy rain.
Flag carrier Cathay Pacific said almost all its flights between 6am and 5pm local time on Wednesday would be axed.
Hong Kong Airlines has also cancelled all its flights from 7am to 5pm and other carriers have already posted cancellations to their schedules.
The Hong Kong Airport Authority said passengers should confirm their flights before heading to the airport.
"As typhoon Hato gradually approaches, flights at the Hong Kong International Airport will be affected all day tomorrow," it said.
Cathay said wind speed and direction was "severely impacting flight operations" in a statement on its website, although it added operations remained normal on Tuesday night.
The observatory raised its Typhoon 3 warning on Tuesday evening, triggered when wind speeds are expected to hit between 41 and 62 kilometres per hour.
It predicted it would raise it to a Typhoon 8, the third-highest warning level, around midnight.
Hong Kong is regularly hit by typhoons between July and October.
The city saw its strongest storm in 1962 when the eye of typhoon Wanda passed over and gusts of 284 kilometres per hour were recorded.
It killed 130 people and destroyed thousands of residential huts, leaving 72,000 people homeless.
Since then, Hong Kong has adapted to typhoons, including making sure its highest commercial skyscrapers can sway in the wind, and they now rarely cause deaths.
