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 signifies a gentle decline in Jeju's average high-temperature, easing from a warm 29.8°C (85.6°F) in August to a still moderately hot 25.8°C (78.4°F). In Jeju, the September nights cool down to an average low of 20.4°C (68.7°F).

Humidity

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

Rainfall

In September, 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, South Korea, the average seawater temperature in September is 24.7°C (76.5°F).
Note: Swimming in 24.7°C (76.5°F) water can be enjoyable based on one's cold tolerance and conditions like sunshine, wind, and ambient temperature. (Olympic swimmers compete in waters between 25°C (77°F) and 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 is 5.4h.

UV index

In September, the average daily maximum UV index is 8. A UV Index estimate of 8 to 10 represents a very high health vulnerability from exposure to the Sun's UV rays for the average person.
Note: The UV index of 8 during September translates into the following guidance:
Be vigilant. Without due care, eyes and skin can be harmed in no time. Between 10 a.m. and 4 p.m., UV radiation is strongest. Make an effort to avoid direct sunlight during this time, remembering that shade structures may not provide full sun protection. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays. Stay alert! Reflective properties of sand and water amplify the Sun's UV radiation.