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. 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

With the beginning of September, the average high-temperature shows a small decrease, transitioning from 29.8°C in August to a still moderately hot 25.8°C. In Jeju, an average temperature of 20.4°C is noted during September nights.

Humidity

The average relative humidity in September in Jeju is 73.7%.

Rainfall

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

Sea temperature

In Jeju, the average seawater temperature in September is 24.7°C.
Note: The cold tolerance of an individual, along with sunshine, wind, and the temperature of the environment, affects the enjoyment of swimming in 24.7°C waters. (Olympic swimmers participate in waters ranging from 25°C to 28°C.)

Daylight

In September, the average length of the day in Jeju is 12h and 23min.
On the first day of the month, sunrise is at 06:07 and sunset at 19:00. On the last day of September, in Jeju, sunrise is at 06:27 and sunset at 18:21 KST.

Sunshine

In Jeju, the average sunshine in September is 5.4h.

UV index

In Jeju, South Korea, 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 ordinary person.
Note: In September, the maximum UV index of 8 transforms into these recommendations:
Without proper safety measures, skin and eyes can be quickly harmed. Be sure to protect yourself. Avoid direct Sun exposure from 10 a.m. to 4 p.m., a period when UV radiation is most intense, and remember that not all shade structures provide full protection. Sun-related eye harm can be minimized with proper sunglasses offering UVA and UVB coverage. Be alert! The reflection of water and sand augments UV radiation intensity.