September weather forecast
Jeju, South Korea

The tingling heat of summer begins to wane in September in Jeju, with temps peaking at 25.8°C (78.4°F). As the month progresses, the searing heat gives way to milder conditions, setting in a pre-autumn ambiance. While the beginning of September still retains the summer vibrancy, the latter half witnesses the autumnal transformation of the verdant landscapes into stunning palettes of yellow and orange. Despite still being wetter than preceding months, the rainfall lessens, paving the way for clearer skies and breezy afternoons. Visitors in September get to experience two seasons in a single month, adding unique twofold allure to their Jeju adventure.

Temperature

September's onset introduces a mild reduction in the average high-temperature, from 29.8°C (85.6°F) in August to a still moderately hot 25.8°C (78.4°F). Jeju experiences a nighttime temperature average of 20.4°C (68.7°F) during September.

Humidity

In September, the average relative humidity is 73.7%.

Rainfall

In September, in Jeju, South Korea, the rain falls for 10.8 days. Throughout September, 222mm (8.74") of precipitation is accumulated. In Jeju, during the entire year, the rain falls for 130.2 days and collects up to 1498mm (58.98") of precipitation.

Sea temperature

In Jeju, the average seawater temperature in September is 24.7°C (76.5°F).
Note: 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. (FYI: The official water temperature required for the Olympic swimming competition is 25°C (77°F) to 28°C (82.4°F).)

Daylight

The average length of the day in September is 12h and 23min.
On the first day of the month, sunrise is at 06:08 and sunset at 18:59. On the last day of September, sunrise is at 06:27 and sunset at 18:20 KST.

Sunshine

The average sunshine in September in Jeju is 5.4h.

UV index

The average daily maximum UV index in September is 8. A UV Index value of 8 to 10 symbolizes a very high health vulnerability from exposure to the Sun's UV radiation for the average person.
Note: In September, a regular UV index of 8 translates into these guidelines:
Take important precautions because unprotected skin can burn and be harmed swiftly. Stay out of direct sunlight between 10 a.m. and 4 p.m., when UV radiation is most intense, and remember that not all shade structures provide complete protection. Employ a hat with a wide brim for robust protection, cutting UV exposure by half. Be on guard! The reflective nature of sand and water boosts UV exposure.