October to December
The best of the year and the reason to time a trip. Dry, mild — around 19 to 26°C — with low humidity and the clearest air, which matters because the Peak view frequently is not there in summer haze.
This is peak season for hotels.
January and February
Cool, sometimes genuinely cold by local standards at 10 to 15°C, and often grey with low cloud that sits on the Peak. Cheap, and the hiking is at its best.
Chinese New Year falls in this window and is the one thing to check. A great many restaurants and shops close for three to five days, transport is packed, and prices rise. It is also spectacular — flower markets, a night parade, lion dances and fireworks over the harbour.
March to May
Warming and increasingly humid, with sea fog in March and April that can close in for days. The Rugby Sevens in late March or April fills the city.
June to September
Hot and very humid — around 28 to 33°C with humidity above 80 per cent — and typhoon season.
Everything still works. Plan around indoor middles of the day, and check the Hong Kong Observatory daily.
Typhoon signals
Hong Kong runs a numbered warning system that everyone watches: 1 (standby), 3 (strong wind), 8 (gale, in four directional variants), 9 and 10 (hurricane).
At signal 8 and above the city shuts — offices and schools close, most transport stops, ferries are suspended and shops shutter. You should be indoors, and hotels will tell you so.
There are also rainstorm warnings — amber, red and black — with black meaning severe flooding and landslide risk.
Both are published constantly and are worth checking each morning between May and October.
Air quality
Variable, and worse when the wind comes from the north across the Pearl River Delta. It has improved substantially since the 2000s. The government publishes an Air Quality Health Index; on high days the Peak view goes and anyone with respiratory sensitivity will notice.
The festival calendar
Chinese New Year — January or February. Tin Hau Festival — April or May, with bamboo theatres and Cantonese opera in fishing villages. Cheung Chau Bun Festival — late April or May, with the bun towers. Dragon Boat Festival — June, with races across the territory. Hungry Ghost Festival — August, with street offerings and opera. Mid-Autumn Festival — September or October, with lanterns and the fire dragon dance in Tai Hang.
Most follow the lunar calendar, so check the dates against your year.