September weather forecast
São Tomé, São Tomé and Príncipe

September is where variations start to show up in São Tomé weather. With a slight increase in temperature range from 21.3°C (70.3°F) to 28.6°C (83.5°F) compared to August, the dynamism becomes more palpable. The relative humidity sees an almost imperceptible increase, coupled with occasional drizzle. Yet, sunshine hours remain unaffected, cutting through the clouds and accentuating the beauty of the city.

Temperature

With the onset of September in São Tomé, a modest change to a still moderately hot 28.6°C (83.5°F) from August's 27.7°C (81.9°F) is noted in high-temperature. September nights experience a consistent temperature drop to a pleasant 21.3°C (70.3°F).

Heat index

For most parts of September, the heat index is calculated to be a hot 33°C (91.4°F). Apply extra caution, heat cramps and heat exhaustion could happen. Heatstroke might occur with long-duration activity.
In reference to the heat index, it's for places in shade and with a slight wind. The heat index has the potential to rise by 15 Fahrenheit (8 Celsius) degrees with direct sunshine exposure.
Note: The heat index, also known as 'real feel' or 'feels like', gives a temperature feeling by integrating air temperature and humidity. One's weather perception can be influenced by a range of factors including metabolic differences, being pregnant, and their level of physical activity. Awareness is key; direct sunlight can enhance the weather's impact, possibly boosting the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values hold great significance to children. Young people are generally more susceptible than adults because they perspire less. Furthermore, their proportionally larger skin surface to their petite bodies and the increased heat output from their actions add to the risk.

Humidity

In September, the average relative humidity is 79%.

Rainfall

In São Tomé, in September, it is raining for 6 days, with typically 17mm (0.67") of accumulated precipitation. In São Tomé, during the entire year, the rain falls for 94 days and collects up to 885mm (34.84") of precipitation.

Sea temperature

In São Tomé, in September, the average water temperature is 26°C (78.8°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

In São Tomé, the average length of the day in September is 12h and 7min.
On the first day of September, sunrise is at 05:29 and sunset at 17:36. On the last day of the month, sunrise is at 05:19 and sunset at 17:26 GMT.

Sunshine

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

UV index

January through May, August through December, 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 health hazard from exposure to the Sun's UV radiation for the average person.
Note: An average maximum UV index of 12 in September leads to these recommendations:
Enforce all necessary precautions, unprotected skin might burn swiftly. Be aware that the sun's UV radiation is strongest between 10 a.m. and 4 p.m. and try to reduce direct sun exposure during this period as much as possible. Prioritize a wide-brim hat for comprehensive sun defense for your face, neck, eyes, and ears. Applying and reapplying liberally a broad-spectrum sunscreen of SPF 30+ every two hours, and straight after a swim or outdoor activity is recommended. Be cautious! Sand and water surfaces make the Sun's UV rays more potent.