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

The arrival of September corresponds with a light shift in temperature, down from 29.8°C (85.6°F) in August to a still warm 25.8°C (78.4°F). During the month of September, the nighttime temperature falls to an average of 20.4°C (68.7°F).

Humidity

In September, the average relative humidity is 73.7%.

Rainfall

In Jeju, in September, it is raining for 10.8 days, with typically 222mm (8.74") of accumulated precipitation. 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, in September, the average water temperature is 24.7°C (76.5°F).
Note: Individual cold sensitivities, influenced by sunshine, wind, and the ambient temperature, play a role in finding a swim in 24.7°C (76.5°F) water pleasant. (Olympic swimming events mandate water temperatures from 25°C (77°F) to 28°C (82.4°F).)

Daylight

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

Sunshine

The average sunshine in September in Jeju is 5.4h.

UV index

In September, the average daily maximum UV index is 8. A UV Index reading of 8 to 10 represents a very high health hazard from exposure to the Sun's UV rays for the average person.
Note: A maximum UV index of 8 in September translates into the following recommendations:
Take all necessary measures. Eyes and skin are at risk if left unprotected. Avoid direct sunlight between the hours of 10 a.m. and 4 p.m., when UV radiation is at its peak. Keep in mind that shade structures may not provide complete protection. For optimum UV protection, wear sun-resistant attire complemented with a hat and quality shades. Warning! Sand and water reflections boost the intensity of UV exposure.