September weather forecast
Waipahu, HI

The month of September in Waipahu, Hawaii witnesses a slight decrease in temperature from the highs of summer, with the maximum temperature recorded as 82°F (27.8°C). Nonetheless, the tropical climate continues to prevail, making it an excellent time to visit the city. As we move into autumn, rainfall begins to pick up, with the month recording an average of 1.46" (37mm). However, September remains a sunny month, ample daylight contributing to outdoor explorations. An interesting weather detail observed this month is the sea temperature, hitting a high of 80.6°F (27°C), making beach visits and aquatic activities quite a lure.

Temperature

Waipahu's temperatures tend to hit their maximum during August and September, with an average high-temperature of 82°F (27.8°C).

Heat index

September's heat index is appraised at a tropical 87.8°F (31°C). Extended exposure and activity might lead to tiredness, potentially resulting in heat cramps.
Heat index's context suggests values are appropriate for shady areas and slight breezes. Heat index values might soar by up to 15 Fahrenheit (8 Celsius) degrees with exposure to direct sunshine.
Note: The heat index, also known as 'feels like' or 'apparent temperature', provides an understanding of perceived warmth by combining temperature and relative humidity. Factors encompassing physical activity, clothing, and metabolic differences have a role in shaping the individual's impression of temperature. Consider that direct sun exposure can intensify the felt heat, adding potentially 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values are quite important for babies and toddlers. Younglings are generally more in peril than adults due to their reduced perspiration. Coupled with a larger skin surface relative to their tiny bodies and greater heat production because of their activity, they become more at risk.

Humidity

April through June and September, with an average relative humidity of 74%, are the least humid months.

Rainfall

In Waipahu, during September, the rain falls for 19.5 days and regularly aggregates up to 1.46" (37mm) of precipitation. Throughout the year, in Waipahu, there are 208.4 rainfall days, and 16.5" (419mm) of precipitation is accumulated.

Ocean temperature

With an average ocean temperature of 80.6°F (27°C), September is the month with the warmest seawater.
Note: Swimming, diving, and other water activities in the temperature range of 77°F (25°C) to 84.2°F (29°C) are perceived as very enjoyable and comfortable for prolonged durations.

Daylight

In Waipahu, Hawaii, the average length of the day in September is 12h and 15min.
On the first day of the month, sunrise is at 6:15 am and sunset at 6:47 pm. On the last day of September, sunrise is at 6:23 am and sunset at 6:20 pm HST.

Sunshine

In September, the average sunshine in Waipahu, Hawaii, is 8.4h.

UV index

September is the month with the highest UV index, with an average maximum UV index of 7. A UV Index reading of 6 to 7 represents a high threat to health from exposure to the Sun's UV rays for average individuals.
Note: The UV index of 7 in September translates into these instructions:
Avert overexposure. Light-skinned people might experience burning in less than 20 minutes. Avoid direct Sun exposure and seek shade between 10 a.m. and 4 p.m., when UV radiation is at its peak, but keep in mind that not all shade structures provide complete protection. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.