High season, from September through late December, sees sunny, dry days and cool, comfortable nights. January and February are mostly cool and damp, with periods of overcast skies. March and April are pleasant, and by May the temperature is consistently warm and comfortable.
June through August are the cheapest months for one reason: they coincide with the hot, sticky, and very rainy typhoon (hurricane) season. Hong Kong is prepared for blustery assaults; if a big storm approaches, the airwaves crackle with information, and your hotel will post the appropriate signals (a No. 10 signal indicates the worst winds; a black warning means a rainstorm is brewing). This is serious business—bamboo scaffolding and metal signs can hurtle through the streets, trees can break or fall, and large areas of the territory can flood. Museums, shops, restaurants, and transport shut down at signal No. 8, but 7-Elevens and cinemas typically stay open.