The first month of the autumn, September
, is still a hot month in Willemstad
, with an average temperature ranging between min 26.5°C (79.7°F) and max 32.6°C (90.7°F).
The ideal sea water temperature of 29°C (84.2°F) and only 4.6 rainfall days, with 48.6mm (1.91") of accumulated rainfall, makes September the best time for swimming and other water activities.
The warmest month is September, with an average high-temperature of 32.6°C (90.7°F) and an average low-temperature of 26.5°C (79.7°F).
In September, the average heat index is evaluated at a life-threatening hot 45.4°C (113.7°F). Beware
: Heat cramps and heat exhaustion are very likely. Heatstroke is imminent with prolonged activity.
Note that heat index values are valued for light wind and location in the shade. With 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', 'felt air temperature', 'real feel', or 'feels like', is a measure that combines 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 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.
The human body normally cools itself by perspiration. Excessive warmth is eliminated from the body by evaporation of sweat. Under high air temperature and humidity (high heat index) conditions, perspiration is limited, and the perception of heat is increased. When heat gain surpasses the level the body can shed, body temperature begins to increase, and consequently, overheating and dehydration can occur, with varying severity.
The average relative humidity in September is 77.5%.
In Willemstad, Curaçao, during September, the rain falls for 4.6 days and regularly aggregates up to 48.6mm (1.91") of precipitation. Throughout the year, in Willemstad, there are 69.4 rainfall days, and 553.4mm (21.79") of precipitation is accumulated.
September and October
, with an average sea temperature of 29°C (84.2°F), are months with the warmest seawater.Note
: For any water activity, surface water temperatures between 25°C (77°F) and 29°C (84.2°F) are considered as excellent and extremely pleasant for lengthened periods.
In September, the average length of the day is 12h and 11min.
On the first day of the month, sunrise is at 06:24 and sunset at 18:45. On the last day of September, sunrise is at 06:24 and sunset at 18:26 AST.
In September, the average sunshine is 8.6h.
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 unprotected exposure to Sun's UV rays for the ordinary person.Note
: In September, the average maximum UV index of 12 translate into the following recommendations:
Take all necessary precautions, as unprotected skin 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. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Even on cloudy days, a sunscreen with a minimum 30 sun protection factor should be generously applied and frequently re-applied, including after every swim or outdoor exercise. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.