Organisers of the cross-harbour swim scheduled for Sunday said the race will be cancelled in the event of a tropical cyclone warning signal.

They said the annual swim will be called off if the Standby Signal No 1 or above, or the red or black rainstorm warning, is in force at 6am that day.

It will also be cancelled if there's a red tide at the harbour, or any other condition that deems the race unsuitable to take place.

The Observatory said it will issue the Standby Signal No 1 between noon and 3pm on Friday as Super Typhoon Yinxing enters within 800 kilometres of Hong Kong, and according to its current forecast track, the storm will be within 400 kilometres of the SAR from Saturday until Sunday morning.

Organisers of the cross-harbour swim called on all participants to pay attention to the latest situation.

"If the race is cancelled, an official announcement will be made shortly on [our] official website and on [our] social media channels," they said.

More than 4,000 swimmers have signed up for the event due to take place on Sunday morning. They'll make their way from Wan Chai to Tsim Sha Tsui.