September weather forecastHonolulu, HI
September
Weather in September
September’s weather in Honolulu starts to hint at the transition into the slow-cooling late-year period. Despite this entry into fall, temperatures stay consistently high, including the sea temperature peaking at 80.4°F (26.9°C). Matching March, September sees an increase in rainfall to 1.22" (31mm). The UV Index stays consistent, requiring continuous usage of sun protection. With a perfect blend of rain and sunshine, September serves as a pleasant prelude to the autumn season.Temperature
The warmest temperatures occur during September, when averages reach a peak of 81.5°F (27.5°C) and a low of 75.6°F (24.2°C).Heat index
The heat index in September is appraised at a hot 86°F (30°C). Enduring exposure and continuous activity might cause a feeling of tiredness and induce heat cramps.When assessing, remember that heat index measurements are for light winds and shaded spots. Being under direct sunlight might amplify the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'felt air temperature', provides an understanding of perceived warmth by combining temperature and relative humidity. One's perception of temperature is subjective, varying based on their activity and individual heat perception, influenced by factors like wind, clothing, and metabolic variations. Given the impact of direct sunlight, it's noteworthy that the felt temperature can rise by 15 Fahrenheit (8 Celsius) degrees. Heat index values hold great significance to children. Children frequently underestimate the importance of resting and drinking fluids. Thirst is a symptom of advanced dehydration - hence the need to hydrate regularly, especially during protracted physical exercises.
Humidity
April, May, September and November, with an average relative humidity of 74%, are the least humid months.Rainfall
In Honolulu, during September, the rain falls for 17.9 days and regularly aggregates up to 1.22" (31mm) of precipitation. In Honolulu, during the entire year, the rain falls for 197.2 days and collects up to 14.61" (371mm) of precipitation.Ocean temperature
With an average ocean temperature of 80.4°F (26.9°C), September is the month with the warmest seawater.Note: Water temperature ranging from 77°F (25°C) to 84.2°F (29°C) is recognized as warm and pleasant by all, making water activities comfortable and delightful for long durations.
Daylight
In Honolulu, the average length of the day in September is 12h and 15min.On the first day of September, sunrise is at 6:15 am and sunset at 6:47 pm. On the last day of the month, sunrise is at 6:22 am and sunset at 6:19 pm HST.
Sunshine
The average sunshine in September is 8.9h.UV index
The months with the highest UV index are July through September, with an average maximum UV index of 7. A UV Index reading of 6 to 7 represents a high health vulnerability from exposure to the Sun's UV rays for the average person.Note: A daily high UV index of 7 in September leads to these guidelines:
Stay clear of intense sun exposure. Solar protection is of utmost significance. Limit your direct sun exposure, especially between 10 a.m. and 4 p.m., when UV radiation is strongest. Shade structures might not provide complete sun protection. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance. Take heed! Reflections of sand and water make the Sun's UV rays stronger.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Honolulu, HI
- Average high temperature in September: 81.5°F
The warmest month (with the highest average high temperature) is September (81.5°F).
The months with the lowest average high temperature are February and March (75°F).
- Average low temperature in September: 75.6°F
The month with the highest average low temperature is August (75.7°F).
The coldest month (with the lowest average low temperature) is February (69.1°F).
Average pressure in September
Honolulu, HI
- Average pressure in September: 29.97"Hg
The month with the highest atmospheric pressure is April (30.06"Hg).
The months with the lowest atmospheric pressure are September and October (29.97"Hg).
Average wind speed in September
Honolulu, HI
- Average wind speed in September: 9.9mph
The windiest month (with the highest average wind speed) is July (12.1mph).
The calmest month (with the lowest average wind speed) is January (9mph).
Average humidity in September
Honolulu, HI
- Average humidity in September: 74%
The months with the highest relative humidity are February and December (76%).
The months with the lowest relative humidity are April, May, September and November (74%).
Average rainfall in September
Honolulu, HI
- Average rainfall in September: 1.22"
The wettest months (with the highest rainfall) are March and October (1.81").
The driest month (with the least rainfall) is July (0.67").
Average rainfall days in September
Honolulu, HI
- Average rainfall days in September: 17.9 days
The months with the highest number of rainy days are March and October (18 days).
The month with the least rainy days is January (12.6 days).
Average sea temperature in September
Honolulu, HI
- Average sea temperature in September: 80.4°F
The best month for swimming (with the highest average sea temperature) is September (80.4°F).
The coldest month (with the lowest average sea temperature) is March (75.7°F).
Average daylight in September /
Average sunshine in September
Honolulu, HI
- Average daylight in September: 12h and 18min
The month with the longest days is June (Average daylight: 13h and 24min).
The month with the shortest days is December (Average daylight: 10h and 54min).
- Average sunshine in September: 8h and 54min
The month with the most sunshine is June (Average sunshine: 10h and 48min).
The months with the least sunshine are November and December (Average sunshine: 6h and 30min).
Average sunshine days in September
Honolulu, HI
- Average sunshine days in September: 6.9 days
The month with the most sunshine days is January (12.8 days).
The month with the least sunshine days is October (6.3 days).
Average UV index in September
Honolulu, HI
- Average UV index in September: 7
The months with the highest UV index are July, August and September (UV index 7).
The months with the lowest UV index are January, February, March, April, May, June, October, November and December (UV index 6).
Average cloud cover in September
Honolulu, HI
- Average cloud cover in September: 33
The month with the most cloud cover is March (Cloud cover 40).
The months with the least cloud cover are January and September (Cloud cover 33).
Average visibility in September
Honolulu, HI
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
