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

The unfolding of September shows an average high-temperature of a still hot 32.8°C (91°F), indicating a slight variance from August's 32.9°C (91.2°F). During September, Bangkok consistently records a temperature low averaging a warm 25°C (77°F).

Heat index

The heat index for September is evaluated at a life-threatening hot 47°C (116.6°F). Keep alert: Heat cramps and heat exhaustion are probable. Heatstroke is a potential danger with continued physical activity.
For clarity, heat index numbers account for light winds and areas under shade. Direct sunlight has the potential to heighten heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'feels like', is a measure that combines air temperature and relative humidity into a single value that indicates how hot the weather feels. The influence of weather is personal, differing among individuals based on variations in body mass, stature, and the degree of physical exertion. With direct sunlight, be aware that it might enhance the heat sensation, raising the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. Juveniles are regularly less conscious of the need to recuperate and rehydrate. Thirst is a tardy symptom of dehydration - hydration, especially during lengthy physical activities, should be maintained.
Sweat evaporation, driven by perspiration, is the method the human body uses to rid itself of excessive warmth. In conditions of both high temperature and humidity (a high heat index), sweating is limited and the perception of heat is enhanced. If the body retains more heat than it can expel, the increasing temperature can lead to heat-related conditions.

Humidity

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

Rainfall

The month with the most rainfall is September, when the rain falls for 21 days and typically aggregates up to 334mm (13.15") of precipitation.

Sea temperature

In Bangkok, the average seawater temperature in September is 28.8°C (83.8°F).
Note: For activities in the water such as swimming or diving, temperatures from 25°C (77°F) to 29°C (84.2°F) are considered optimal for prolonged enjoyment without discomfort.

Daylight

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, in Bangkok, sunrise is at 06:07 and sunset at 18:08 +07.

Sunshine

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

UV index

The months with the highest UV index are February through September, with an average maximum UV index of 12. A UV Index estimate of 11, and higher, represents an ultimate health vulnerability from exposure to the Sun's UV rays for ordinary individuals.
Note: The daily high UV index of 12 during September translates into the following recommendations:
Ensure every key safety measure. People with light skin might sustain burns in fewer than 5 minutes. Between 10 a.m. and 4 p.m., the Sun emits the most powerful UV radiation. Limit direct exposure to the Sun during these hours. By wearing a generously brimmed hat, you can cut UV radiation exposure significantly. Following every swim or outdoor workout, a sunscreen with an SPF of not less than 30 should be liberally applied and re-applied frequently, even on overcast days. Be on guard! The reflective nature of sand and water boosts UV exposure.