The Hong Kong Observatory says it will issue a T1 at 6.40am on Monday as Tropical Cyclone Man-yi moves towards the territory.

The storm is forecast to come within 800 kilometres of the city around midnight on Monday, but is expected to weaken.

However, windy conditions are likely by Tuesday, the Observatory said, warning that some low-lying areas may see minor flooding in some areas because of the northeast monsson and Man-yi, and urged the public to take care.

The Observatory added that depending on the storm's intensity and distance from the city, it may issue a higher warning signal on Monday night or early Tuesday.