🇭🇰Hong Kong

Hong Kong sits at 22°15′N as a Special Administrative Region of China on the southern coast of Guangdong province, covering approximately 1,114 km² of dramatically hilly terrain with the highest point Tai Mo Shan at 957 m on Hong Kong island and in the New Territories.

The territory comprises Hong Kong island, the Kowloon peninsula, approximately 260 outlying islands—including Lantau, Lamma, and Cheung Chau—and the New Territories backing onto mainland China. Located on the South China Sea coast just inside the Tropic of Cancer, the climate is humid subtropical (Köppen Cwa) with strong Asian monsoon influence, characterized by hot, humid, very wet summers driven by the southwest monsoon and typhoons, and cooler, drier winters dominated by the dry northeast monsoon flow off mainland China.

Hong Kong Observatory averages 16°C in January and 29°C in July, with approximately 2,400 mm of rainfall concentrated almost entirely from May through September and a sharp peak in June–August. Relative humidity rises to 85–90% in summer and drops to 65–70% in winter. Sea-surface temperatures range from around 20°C in February to 28°C in August. Rare snow has fallen on Tai Mo Shan summit.

Hong Kong sits squarely in the western Pacific's typhoon belt — severe typhoon strikes include Wanda in September 1962, a Category 4 storm-surge disaster killing 183 people, Hope in 1979, York in 1999 with the longest typhoon-warning hoist on record, Hato in August 2017 reaching Category 3 with 250 km/h gusts and storm surge, Mangkhut in September 2018 passing as a Category 5 system nearby with 240 km/h gusts, and the extreme black rainstorm event of 7–8 September 2023 when Hong Kong Observatory recorded 158.1 mm in one hour—a record. Sea-level rise and intensifying typhoon storm surges, increasingly severe summer heatwaves, and frequent extreme rainfall events are central concerns for the territory's extensive reclaimed-land coastline.

Our archive covers 2 Hong Kong cities with daily ERA5 reanalysis data going back to 1940. The warmest July averages occur in New Territories, around 30.7°C, while New Territories records the coldest January nights near 12.3°C. Comparing the last decade against the 1940–1970 baseline, mean temperatures across these cities have risen by about 1.2°C.1 mm hourly rainfall record of September 2023, intensifying typhoon storm surges like Hato 2017 and Mangkhut 2018, and increasingly severe summer heatwaves.