September weather forecast
Arroyo, PR

September weather in Arroyo denotes a slight drop in air and sea temperatures. Yet it continues to register the highest rainfall volumes for the year at 4.29" (109mm), which may lead to sporadic interruptions in outdoor activities. As this month commences, the transition from the warm season to slightly cooler temperatures begins. Extended daylight hours persist, yielding abundant time to appreciate the city’s natural wealth and cultural vibrancy. Consistent winds characterize Arroyo's weather in September, making it an essential part of the city's climate portrait.

Temperature

The arrival of September brings an average high-temperature of a still moderately hot 85.1°F (29.5°C), nearly identical to August's 85.3°F (29.6°C). September nights cool to an average low-temperature of 76.3°F (24.6°C), a marginal decrease from its daytime equivalent.

Heat index

The heat index value during September is evaluated at a sweltering 96.8°F (36°C). Adopt heightened preventive measures, heat exhaustion and heat cramps are probable. Persistent activity could lead to heatstroke.
Be informed that the heat index values are oriented around shady conditions and gentle breezes. Heat index values have the potential to be boosted by 15 Fahrenheit (8 Celsius) degrees due to direct sunlight.
Note: The heat index, also known as 'real feel' or 'felt air temperature', comes about by integrating the temperature readings with the humidity levels. One's perception of weather can be shaped by other factors, involving metabolic differences, pregnancy, and physical exertion. Should you be directly under the sun, anticipate a possible increase in the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. In general, children are more at risk than adults because they sweat less. Furthermore, the large skin surface compared to their small bodies and the high heat production due to their actions contribute to this vulnerability.
For the human body, perspiration is the go-to method to regulate temperature, using sweat's evaporation to dissipate warmth. Elevated relative humidity disrupts typical body cooling by reducing the evaporation rate, consequently decreasing the body's cooling rate and enhancing the feeling of heat. If heat absorption isn't effectively countered by the body's cooling methods, body temperature surges, hinting at potential problems.

Humidity

In September, the average relative humidity is 80%.

Rainfall

The month with the most rainfall is September, when the rain falls for 23.7 days and typically aggregates up to 4.29" (109mm) of precipitation.

Ocean temperature

With an average ocean temperature of 85.5°F (29.7°C), September is the month with the warmest seawater.
Note: Surface water temperatures between 77°F (25°C) and 84.2°F (29°C) offer outstanding conditions for any water activity, providing extreme pleasure for extended periods.

Daylight

In Arroyo, the average length of the day in September is 12h and 14min.
On the first day of the month, sunrise is at 6:10 am and sunset at 6:37 pm. On the last day of September, sunrise is at 6:14 am and sunset at 6:13 pm AST.

Sunshine

In September, the average sunshine is 9h.

UV index

The months with the highest UV index are May through October, with an average maximum UV index of 7. A UV Index of 6 to 7 symbolizes a high threat to health from exposure to the Sun's UV radiation for ordinary individuals.
Note: In September, the average maximum UV index of 7 translates into the following recommendations:
Guard against overexposure. Protection from sun-induced harm is essential. Limit direct sun exposure and seek shade between 10 a.m. and 4 p.m., the time of the most intense UV radiation, noting that shade structures may not provide total sun protection. A hat with a broad brim is indispensable, filtering out up to half of UV rays. Attention! The reflection of both water and sand can increase the intensity of UV rays.