Winters are generally very mild, with daytime temperatures of 18-22°C (64–72°F) but with nights dipping into 10°C (50°F) and below sometimes, especially in the countryside. Christmas in Hong Kong is considered warm compared with many other Northern Hemisphere countries. Chinese New Year is notorious for cold (10°C/50°F), wet weather; this is because winter in Hong Kong tends to start out mild and dry and then turn a bit cool and wet later, though the cool weather is brief.
Spring (March-May) and autumn (September-November/December) have average temperature between 21-24°C (70-5°F). Autumn is probably a more comfortable season as spring tends to be more humid and rainy.
Although most buildings in Hong Kong have air-conditioning to cope with the summer weather, winter heating is something of a novelty. During the coldest days, most locals simply wear more layers even indoors. In a restaurant for example, it is not unusual to see customers eating with their jackets and scarves on.