September weather forecast
Bangkok, Thailand

With the arrival of September, Bangkok, Thailand reaches the final stretch of the monsoon season. This period sees the highest level of relative humidity at 79%, making it the most humid month of the year. Despite continued rainfall, a gradual fall in sea temperatures and an overall decrease in sunlight hours characterizes the transition period. Slightly cooling temperatures provide relief from the intense heat experienced earlier in the year. The beckoning of the dry season's arrival is felt as the city moves into October.

Temperature

During September, Bangkok records an average high-temperature of a still tropical 32.8°C, marking a slight divergence from August's 32.9°C. September nights in Bangkok experience a consistent temperature drop to a warm 25°C.

Heat index

September's average heat index is computed to be a life-threatening hot 47°C. Precaution: Heat cramps along with heat exhaustion are possible. Heatstroke is a serious risk with continued exertion.
One should consider that heat index numbers are for shaded settings and light wind. The heat index has the possibility to be enhanced by 15 Fahrenheit (8 Celsius) degrees when there is direct sun exposure.
Note: The heat index, also known as 'real feel' or 'apparent temperature', evaluates the perceived heat by adding the effect of moisture in the air. An individual's perception of weather can be swayed by a variety of elements including metabolic differences, pregnancy status, and their level of physical exertion. Be mindful that being in direct sunlight might mean feeling hotter, with the heat index rising by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for babies and toddlers. Kids are usually more vulnerable than adults, given their lesser sweating ability. Along with their larger skin surface relative to their small stature and the excess heat due to their activity, their risk is amplified.
To offset high temperatures, the human body releases sweat which, upon evaporation, cools it down. Elevated relative humidity disrupts typical body cooling by reducing the evaporation rate, consequently decreasing the body's cooling rate and enhancing the feeling of heat. When body temperature rises due to an imbalance in heat gain, there's a potential for dehydration and overheating.

Humidity

September is the most humid month, with an average relative humidity of 79%.

Rainfall

September is the month with the most rainfall. Rain falls for 21 days and accumulates 334mm of precipitation.

Sea temperature

In Bangkok, the average seawater temperature in September is 28.8°C.
Note: Water activities including swimming and diving are pleasurable in temperatures between 25°C and 29°C, ensuring comfort and enjoyment for extended time frames.

Daylight

In Bangkok, the average length of the day in September is 12h and 13min.
On the first day of the month, sunrise is at 06:06 and sunset at 18:29. On the last day of September, sunrise is at 06:07 and sunset at 18:09 +07.

Sunshine

August and September, with an average of 5.2h of sunshine, are months with the least sunshine in Bangkok.

UV index

February through September, with an average maximum UV index of 12, are months with the highest UV index. A UV Index reading of 11, and higher, represents an extreme health hazard from exposure to the Sun's UV radiation for the average person.
Note: During September, 12 as the daily maximum UV index converts into the following advice:
Take all critical precautions, unprotected skin might burn 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. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage. Even on overcast days, apply and frequently reapply a sunscreen with SPF 30 or more, specifically after a swim or outdoor workout. Caution! The mirror effect of sand and water ups the UV radiation strength.