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 in Bangkok shows an average high-temperature of a still tropical 32.8°C (91°F), indicating a slight variance from August's 32.9°C (91.2°F). Bangkok experiences an average nighttime temperature of 25°C (77°F) in the month of September.

Heat index

For September, the heat index is estimated at a burning hot 47°C (116.6°F). Stay watchful: Heat exhaustion along with heat cramps are likely. Ongoing effort may cause heatstroke.
It is emphasized that the heat index's values are meant for shaded zones with mild winds. The heat index could see an increase by 15 Fahrenheit (8 Celsius) degrees under direct sunshine.
Note: The heat index, also known as 'felt air temperature' or 'real feel', reflects the blend of air temperature and relative humidity to give a temperature impression. 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. When exposed to direct sunlight, it's possible for the heat index to increase by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values hold particular importance for children. Children often fail to understand the importance of rest and rehydration. Thirst is a late manifestation of dehydration - hence, it is crucial to stay hydrated, especially during ongoing physical activities.
For the human body, perspiration is the go-to method to regulate temperature, using sweat's evaporation to dissipate warmth. When the level of relative humidity is elevated, evaporation diminishes, causing more warmth to be retained in the body than in dry air. Potential thermal conditions emerge as the body's heat gain outpaces its cooling mechanisms.

Humidity

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

Rainfall

September is the month with the most rainfall. Rain falls for 21 days and accumulates 334mm (13.15") of precipitation.

Sea temperature

In Bangkok, in September, the average water temperature is 28.8°C (83.8°F).
Note: Water activities in temperatures ranging from 25°C (77°F) to 29°C (84.2°F) are pleasurable, without feeling uncomfortable even during extended periods.

Daylight

In September, the average length of the day 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 18:08 +07.

Sunshine

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

UV index

February through September, with an average maximum UV index of 12, are months with the highest UV index. A UV Index estimate of 11, and higher, represents an extreme threat to health from exposure to the Sun's UV radiation for ordinary individuals.
Note: The daily high UV index of 12 during September translates into the following recommendations:
Enforce every vital precaution. Those with light skin could endure burns in a matter of minutes. Avoid direct exposure to the Sun between 10 a.m. and 4 p.m., the peak period for UV radiation, noting that objects like parasols or canopies might not offer complete sun protection. It's wise to wear UVA and UVB-blocking sunglasses when the sun shines brightly. Sunscreen with a sun protection factor of no less than 30 should be used liberally and reapplied frequently on overcast days, including after every swim or outdoor activity. Take heed! Reflections of sand and water make the Sun's UV rays stronger.