Steep terrain has forced about 90 percent of Hong Kong's population to congregate in just 15 percent of the land area, creating the highest population density in the world. With no place to expand but upward, Hong Kong has some of the world's tallest buildings outside New York City. Much of the territory, however, is uninhabited government parkland, and some of it is still wild. It has many snakes, and the bird population on Hong Kong Island includes a large community of escaped domestic parakeets and their offspring. Hong Kong's tropical latitude produces high temperatures most of the year and a short, mild winter.
Spring is extremely wet, often causing dangerous landslides and floods.
Autumn is extremely dry. Hill fires have burned entire communities of crowded squatter huts put up by refugees. The most significant weather event is the typhoon season of late summer. The major spurt in Hong Kong's population growth was in the latter part of the 1970s, when it swelled from about 4 million to 5 million. This was the result of an influx both from China and from Vietnam following the fall of Saigon in 1975.