Jeju
South Korea
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Jeju, South Korea

A high sunrise Panorama of the Jeju Island in Jeju, South Korea
A high sunrise Panorama of the Jeju Island in Jeju, South Korea
The first month of the autumn, September, is also a moderately hot month in Jeju, South Korea, with average temperature fluctuating between 20.4°C (68.7°F) and 25.8°C (78.4°F).

Temperature

In Jeju, the average high-temperature slightly decreases, from a warm 29.8°C (85.6°F) in August, to a still moderately hot 25.8°C (78.4°F). In September, the average low-temperature is 20.4°C (68.7°F).

Humidity

The average relative humidity is 73.7%.

Rainfall

In Jeju, during 10.8 rainfall days, 221.6mm (8.7") of precipitation is typically accumulated. Throughout the year, in Jeju, there are 130.2 rainfall days, and 1497.7mm (59") of precipitation is accumulated.

Sea temperature

In Jeju, the average water temperature is 24.7°C (76.5°F).
Note: For individuals prone to feeling cold, swimming in 23°C (73.4°F) is still regarded as intolerable. A wetsuit is not a necessity, but sunshine, wind, and air temperature are essential factors for relishing swimming at 24.7°C (76.5°F).

Daylight

The average length of the day is 12.4h.

Sunshine

The average sunshine in Jeju is 5.4h.

UV index

In Jeju, the average daily maximum UV index in September is 8. A UV Index of 8 to 10 symbolizes a very high health hazard from unprotected exposure to the Sun's UV rays for ordinary individuals.
Note: In September, the average maximum UV index of 8 translate into the following recommendations:
Take extra precautions. Protection against sun damage is required. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.

What is the temperature in September in Jeju?

In Jeju, South Korea, in September, the average high-temperature is 25.8°C (78.4°F), and the average low-temperature is 20.4°C (68.7°F).

What is the average humidity in September in Jeju?

In September, the average relative humidity in Jeju is 73.7%.

How much does it rain in Jeju in September?

In Jeju, in September, during 10.8 rainfall days, 221.6mm (8.7") of precipitation is typically accumulated.

What is the sea temperature in September in Jeju?

In September, the average sea temperature in Jeju, South Korea, is 24.7°C (76.5°F). Depending on a person's sensitivity to cold, with regards to sunshine, wind, and air temperature, a quick swim in 24.7°C (76.5°F) water may be enjoyable.

How many hours of daylight does Jeju have in September?

In September, the average length of the day in Jeju, South Korea, is 12.4h.

How many hours of sunshine does Jeju have in September?

The average sunshine in September in Jeju is 5.4h.

What is the UV index reading in September in Jeju?

The average daily maximum UV index in September in Jeju, South Korea, is 8. A UV Index value of 8 to 10 symbolizes a very high health vulnerability from unprotected exposure to the UV radiation.
Average temperature in September - Jeju, South Korea
  • Average high temperature in September: 25.8°C

The warmest month (with the highest average high temperature) is August (29.8°C).
The month with the lowest average high temperature is January (8.3°C).

  • Average low temperature in September: 20.4°C

The month with the highest average low temperature is August (24.3°C).
The coldest month (with the lowest average low temperature) is January (3.2°C).

Average humidity in September - Jeju, South Korea
  • Average humidity in September: 73.7%

The month with the highest relative humidity is July (78.3%).
Months with the lowest relative humidity are February and March (64.9%).

Average rainfall in September - Jeju, South Korea
  • Average rainfall in September: 221.6mm

The wettest month (with the highest rainfall) is August (262.5mm).
The driest month (with the lowest rainfall) is December (47.7mm).

Average rainfall days in September - Jeju, South Korea
  • Average rainfall days in September: 10.8 days

The month with the highest number of rainy days is August (13.5 days).
The month with the lowest number of rainy days is October (7 days).

Average sea temperature in September - Jeju, South Korea
  • Average sea temperature in September: 24.7°C

The best month for swimming (with the highest average sea temperature) is August (26.2°C).
The coldest month (with the lowest average sea temperature) is March (13.3°C).

Average daylight in September / Average sunshine in September - Jeju, South Korea
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.4h).
The month with shortest days is December (Average daylight: 10h).

  • Average sunshine in September: 5.4h

The month with most sunshine is May (Average sunshine: 6.8h).
The month with least sunshine is January (Average sunshine: 2.3h).

Average UV index in September - Jeju, South Korea
  • Average UV index in September: 8

The month with the highest UV index is July (UV index 11).
Months with the lowest UV index are January and December (UV index 3).