September weather forecast
Ko Samui, Thailand

The weather in Ko Samui, Thailand, in September can be characterized by a slight rise in rainfall to 122mm (4.8") relative to August. This month acts as a link between the rainy season and the impending drier period. Beaches retain their charm with sea temperature and daylight hours holding steady. This trend in weather serves as a precursor to the heavy rains expected in the months subsequent. Tourists can revel in this month’s relatively balanced weather.

Temperature

September's commencement is accompanied by an average high-temperature of a still hot 30.5°C (86.9°F), diverging marginally from August's 31.7°C (89.1°F). September nights in Ko Samui, Thailand, are marked by an average temperature drop to a moderately hot 24.8°C (76.6°F).

Heat index

Throughout September, the heat index is computed to be a torrid 39°C (102.2°F). Undertake special precautions, the probability of heat exhaustion and heat cramps is high. Prolonged activity may provoke heatstroke.
From a standpoint of the heat index, values pertain to shaded conditions and mild breezes. The direct sunshine could escalate the heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'feels like', determines the feeling of heat when you account for the relative humidity. Elements of metabolic variation, physical activity, and clothing contribute to the effect of temperature on an individual. Recognize that direct exposure to the sun can escalate the heat effect, potentially adding 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values hold particular significance for children. Young individuals are typically more threatened than adults due to their reduced perspiration. Also, the larger skin surface proportionate to their small bodies and the increased heat from their activities magnify their risk.
The physiological way the human body responds to excessive heat is by inducing perspiration, using sweat evaporation as a cooling mechanism. With high air temperature and humidity (high heat index) conditions, sweat production is restricted, leading to an amplified perception of heat. Rising body temperatures resulting from an imbalance in heat absorption can lead to potential thermal issues.

Humidity

In Ko Samui, the average relative humidity in September is 80%.

Rainfall

In September, the rain falls for 16 days. Throughout September, 122mm (4.8") of precipitation is accumulated. In Ko Samui, during the entire year, the rain falls for 160 days and collects up to 1960mm (77.17") of precipitation.

Sea temperature

In September, the average sea temperature in Ko Samui is 29.2°C (84.6°F).
Note: Swimming, diving, and other water endeavors at temperatures between 25°C (77°F) and 29°C (84.2°F) are considered enjoyable and satisfying for extended periods without discomfort.

Daylight

In September, the average length of the day is 12h and 11min.
On the first day of September, sunrise is at 06:10 and sunset at 18:28. On the last day of the month, sunrise is at 06:08 and sunset at 18:11 +07.

Sunshine

The months with the least sunshine are May through December, with an average of 6h of sunshine.

UV index

February through October, with an average maximum UV index of 12, are months with the highest UV index. A UV Index of 11, and more, symbolizes an ultimate health vulnerability from exposure to the Sun's UV radiation for the ordinary person.
Note: A maximum daily UV index of 12 during September morphs into the following directions:
Practice all-important precautions. Light skin people may get burned in less than 5 minutes. The Sun emits the most powerful UV radiation between 10 a.m. and 4 p.m. Try to avoid direct sunlight during this period. Arm yourself against UV rays' harm with protective apparel and UV-filtering shades. After every outdoor workout or swim, liberally apply and frequently reapply a broad-spectrum SPF 30+ sunscreen. Alert! The Sun's UV rays are heightened by the reflection of sand and water.