September weather forecast
Hong Kong, Hong Kong

With the onset of September, Hong Kong begins to witness a noticeable retraction from the extreme summer conditions. Although the arrival of autumn is greeted with much-needed relief from the sweltering heat, the weather predominantly remains warm. The rainfall levels for the month decrease significantly from the highs of August to 328mm (12.91"). As the month progresses, a gentler, more pleasant climate begins to settle in, assuaging the high heat and humidity of the last few months.

Temperature

The commencement of September brings an average high-temperature of a still hot 30.1°C (86.2°F), marking an inconsequential divergence from August. Nighttime temperatures in Hong Kong during September report a consistent average of 25.8°C (78.4°F).

Heat index

The heat index value for September is calculated to be a torrid 37°C (98.6°F). Adopt special protective actions against heat exhaustion and heat cramps. Long-duration activity risks heatstroke.
In reference to the heat index, it's for places in shade and with a slight wind. Exposure to the sun directly might heighten the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'feels like', is a numerical representation of warmth when taking temperature and moisture levels into account. The effect is experienced differently by individuals, hinging on unique characteristics such as body mass, stature, and level of activity. Direct sun rays have a notable impact on perceived temperature, which can raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical for babies and toddlers. Youngsters typically face more danger than adults since they sweat less. Their larger skin surface compared to their small bodies and heightened heat production from their activities augment their vulnerability.
Perspiration and the resultant sweat evaporation are the body's natural thermostat, helping regulate temperature. Elevated relative humidity diminishes evaporation, thereby reducing the body's ability to shed heat and creating a feeling of being too warm. As body temperatures escalate without effective heat release, one might face dehydration threats.

Humidity

In September, the average relative humidity is 78%.

Rainfall

In Hong Kong, in September, during 14.7 rainfall days, 328mm (12.91") of precipitation is typically accumulated. In Hong Kong, Hong Kong, during the entire year, the rain falls for 137.8 days and collects up to 2398mm (94.41") of precipitation.

Sea temperature

In September, the average sea temperature is 28.3°C (82.9°F).
Note: Temperatures between 25°C (77°F) and 29°C (84.2°F) in water are ideal for swimming, diving, and other activities, providing enjoyment and comfort for extended durations.

Daylight

In September, the average length of the day in Hong Kong is 12h and 17min.
On the first day of the month, sunrise is at 06:06 and sunset at 18:40. On the last day of September, in Hong Kong, sunrise is at 06:14 and sunset at 18:12 HKT.

Sunshine

In Hong Kong, the average sunshine in September is 5.7h.

UV index

In September, the average daily maximum UV index in Hong Kong is 11. A UV Index estimate of 11, and higher, represents an excessive health risk from exposure to the Sun's UV rays for the ordinary person.
Note: In September, the maximum UV index of 11 suggests these recommendations:
Employ every crucial safety step. Those with fair skin could experience burns in a matter of minutes. The Sun's UV radiation is at its strongest between the hours of 10 a.m. and 4 p.m. Minimize direct exposure to the sun during this period. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes. Even if it's cloudy, generously apply and frequently reapply a sunscreen with no less than a 30 sun protection factor after each swim or outdoor exercise. Heads up! Sand and water reflection magnifies the UV exposure from the Sun.