São Tomé
São Tomé and Príncipe
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
São Tomé, São Tomé and Príncipe

Clear blue water crashing on the big shore rocks on the beach in São Tomé, São Tomé and Principe, with palm trees along the beautiful beach
Clear blue water crashing on the big shore rocks on the beach in São Tomé, São Tomé and Principe, with palm trees along the beautiful beach
The first month of the autumn, September, is still a warm month in São Tomé, São Tomé and Príncipe, with average temperature ranging between max 28.6°C (83.5°F) and min 21.3°C (70.3°F).

Temperature

In São Tomé, the average high-temperature in September is essentially the same as in August - a still warm 28.6°C (83.5°F). In September, the average low-temperature is 21.3°C (70.3°F).

Heat index

The average heat index is estimated at a tropical 33.5°C (92.3°F). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
Take into consideration that the heat index values are calculated for shade and light wind conditions. With the exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature', 'feels like', 'felt air temperature', or 'real feel', is a measure that combines both air temperature and relative humidity into a single value that indicates how hot the weather feels. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (differences in body mass, height, and shape, clothing, wind). Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.

Humidity

In September, the average relative humidity in São Tomé is 79%.

Rainfall

In São Tomé, during 6 rainfall days, 17mm (0.67") of precipitation is typically accumulated. Throughout the year, in São Tomé, São Tomé and Príncipe, there are 94 rainfall days, and 885mm (34.84") of precipitation is accumulated.

Sea temperature

In September, the average sea temperature is 26°C (78.8°F).
Note: Water temperature between 25°C (77°F) and 29°C (84.2°F) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

Daylight

January through December, with an average of 12.1h of daylight, are months with the longest days. Months with the shortest days in São Tomé are January through December, with an average of 12.1h of daylight.

Sunshine

The average sunshine in São Tomé is 4h.

UV index

Months with the highest UV index are January through May, August through December, with an average maximum UV index of 12. A UV Index of 11, and more, symbolizes an ultimate health vulnerability from unsafe exposure to the UV radiation for average individuals.
Note: In September, the average maximum UV index of 12 translate into the following recommendations:
Take all required precautions, as unprotected skin and eyes can burn in minutes. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. A broad-spectrum sunscreen of SPF 30+ should be liberally applied and re-applied every two hours, and immediately after an outdoor workout or a swim. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.

What is the temperature in September in São Tomé?

In São Tomé, in September, the average high-temperature is 28.6°C (83.5°F), and the average low-temperature is 21.3°C (70.3°F). In September, the average heat index (a.k.a. 'real feel', 'apparent temperature'), that represents influence of the relative humidity to air temperaure, is estimated at 33.5°C (92.3°F).

What is the average humidity in September in São Tomé?

The average relative humidity in September is 79%.

How much does it rain in São Tomé in September?

In São Tomé, São Tomé and Príncipe, during September, the rain falls for 6 days and regularly aggregates up to 17mm (0.67") of precipitation.

How warm is the water in September in São Tomé?

In September, the average sea temperature in São Tomé is 26°C (78.8°F). Water temperature between 25°C (77°F) and 29°C (84.2°F) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

When are the longest days in São Tomé?

Months with the longest days in São Tomé, São Tomé and Príncipe, are January through December, with an average of 12.1h of daylight.

What is the month with the shortest days in São Tomé?

January through December, with an average of 12.1h of daylight, are months with the shortest days.

How many hours of daylight does São Tomé have in September?

In São Tomé, São Tomé and Príncipe, the average length of the day in September is 12.1h.

How many hours of sunshine does São Tomé have in September?

In São Tomé, São Tomé and Príncipe, the average sunshine in September is 4h.

What is the month with the highest UV index in São Tomé?

January through May, August through December, with an average maximum UV index of 12, are months with the highest UV index in São Tomé, São Tomé and Príncipe.

How high is the UV index in September in São Tomé?

In São Tomé, São Tomé and Príncipe, the average daily maximum UV index in September is 12. A UV Index estimate of 11, and higher, represents an extreme health threat from the exposure to the Sun's UV rays.
Average temperature in September - São Tomé, São Tomé and Príncipe
  • Average high temperature in September: 28.6°C

The warmest month (with the highest average high temperature) is March (30.2°C).
The month with the lowest average high temperature is July (27.3°C).

  • Average low temperature in September: 21.3°C

Months with the highest average low temperature are March, April and May (22.6°C).
The coldest month (with the lowest average low temperature) is July (20.4°C).

Average humidity in September - São Tomé, São Tomé and Príncipe
  • Average humidity in September: 79%

Months with the highest relative humidity are January, November and December (85%).
The month with the lowest relative humidity is July (77%).

Average rainfall in September - São Tomé, São Tomé and Príncipe
  • Average rainfall in September: 17mm

The wettest month (with the highest rainfall) is March (131mm).
The driest month (with the lowest rainfall) is July (0mm).

Average rainfall days in September - São Tomé, São Tomé and Príncipe
  • Average rainfall days in September: 6 days

Months with the highest number of rainy days are March and October (12 days).
The month with the lowest number of rainy days is July (2 days).

Average sea temperature in September - São Tomé, São Tomé and Príncipe
  • Average sea temperature in September: 26°C

Best months for swimming (with the highest average sea temperature) are February, March and April (29°C).
The coldest month (with the lowest average sea temperature) is July (25°C).

Average daylight in September / Average sunshine in September - São Tomé, São Tomé and Príncipe
  • Average daylight in September: 12.1h

Months with the longest days are January, February, March, April, May, June, July, August, September, October, November and December (Average daylight: 12.1h).
Months with shortest days are January, February, March, April, May, June, July, August, September, October, November and December (Average daylight: 12.1h).

  • Average sunshine in September: 4h

The month with most sunshine is June (Average sunshine: 5.5h).
The month with least sunshine is October (Average sunshine: 3.7h).

Average UV index in September - São Tomé, São Tomé and Príncipe
  • Average UV index in September: 12

Months with the highest UV index are January, February, March, April, May, August, September, October, November and December (UV index 12).
The month with the lowest UV index is July (UV index 10).