Weather in Hong Kong in September

How September compares

September is the 4th warmest month of the year in Hong Kong and ranks 32nd of 134 destinations we compare for September - see where else is hot in September. Against London's average high of 18.6°C in September, Hong Kong is 10.5°C warmer by day and 14.0°C warmer at night.

Daytime and night-time in September

The typical September day in Hong Kong peaks at 29.1°C, but that is an average: the warmest 10% of days reach 31.0°C or more. About 99% of days top 25°C and 1 in 3 pass 30°C. Nights average 25.2°C; one night in ten drops to 23.7°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest September day here reached 33.9°C (2008-09-22) and the coldest night 18.6°C (1997-09-29).

Rain in September

Wet (more than 8 rainy days): about 17 days with 1 mm or more, 217 mm in total. Year to year it varies a lot - the wettest September was 2020 with 568 mm, the driest 1995 with 82 mm. Humidity averages 83%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in September

The sea averages 28.2°C - warm enough to swim (22°c+). Depending on the year it ranges from 27.6°C to 28.9°C. For the warmest sea here, come in August (28.5°C).

Sunshine and daylight

Around 4.8 hours of sunshine a day (estimated from cloud cover), 12.1 hours of daylight: the sun rises about 06:10 and sets about 18:27 local time in mid-September. Average cloud cover is 60%.

Is September a good time to visit Hong Kong?

It is a reasonable choice: hot days but expect showers. The best months for Hong Kong on our scoring are November, October, September; months averaging 25°C or more: Apr, May, Jun, Jul, Aug, Sep, Oct.

Expect heat that lasts into the evening

September feels considerably hotter than it does at home: Hong Kong's average daytime high is 29.1°C, compared with London's 18.6°C. Humidity averages 83%, so allow for sticky conditions rather than judging comfort by temperature alone. Days reaching 30°C account for 29% of the month, making a slower pace and breaks from the heat sensible. Put more demanding walking earlier in the day and leave room for indoor time around midday. Pack lightweight, breathable clothes and comfortable footwear. With average night lows of 25.2°C, evenings offer limited cooling, so do not expect the temperature to drop enough for a typical UK autumn outfit.

Rain is the main compromise

About 17 rainy days makes September a month for adaptable plans, not a tightly scheduled outdoor holiday. You need not rule it out, but you should be comfortable changing the order of your day when rain arrives. Carry a compact umbrella and choose a lightweight waterproof rather than a heavy coat that could feel uncomfortable in the heat. Footwear that copes with getting wet is useful too. Rainfall varies substantially between years, so the monthly average cannot promise how your trip will turn out. If wet weather would spoil the main reason for travelling, September is a less convincing choice.

Warm sea, but do not count on constant sunshine

The sea averages 28.2°C, making swimming a clear positive if you prefer warm water. That does not make September a dependable sunshine holiday, though: average sunshine is about 4.8 hours within 12.1 hours of daylight. There is plenty of daylight for flexible plans, but sunshine is far from continuous. Keep swimming plans dependent on the day's weather rather than treating warm water as a guarantee of suitable conditions. Overall, September works best for travellers who value warmth and can accept rain and humidity. It ranks behind November and October in the overall monthly recommendations, despite its appealing sea temperature.