Macau's observatory hoisted the standby Signal No. 1 at 5 p.m. today.
According to a statement by the Meteorological and Geophysical Bureau (SMG), a "slowly moving" tropical depression was located about 130 kilometres south-southwest of Macau at 5 p.m.
The hoisting of Signal No. 1 means that a tropical cyclone is centred within 800 kilometres of Macau and may affect the city, according to the observatory.
The weather station said it expected to Signal No. 1 to remain hoisted tonight.
