September weather forecastAgat, GU
September
Weather in September
September is a subtle shift in weather from the peak of summer in Agat, with declining rainfall and slightly lower temperatures. However, the high precipitation levels continue with rainfall reaching 10.28" (261mm), marking the highest rainfall for the year. The average temperatures remain balmy, making the conditions ideal for nature enthusiasts. As we move into October, the weather begins to transition into slightly cooler and tamer conditions, with a decrease in temperature and rainfall.Temperature
The shift into September reveals an average high-temperature of a still warm 84.4°F (29.1°C), closely mirroring August's climate. Agat notes an average temperature descent to a still warm 82.8°F (28.2°C) in September, a small shift from its daytime peak.Heat index
In September, the average heat index is computed to be a tropical 93.2°F (34°C). Adopt additional preventive measures, heat cramps and heat exhaustion are potential outcomes. Prolonged activity may trigger heatstroke.One should consider that heat index numbers are for shaded settings and light wind. Direct sunlight might lead to a heat index increase by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', binds temperature metrics with humidity values to give a sense of the actual warmth. An individual's perception of weather can be affected by a variety of elements including metabolic differences, being pregnant, and their level of physical exertion. By being directly under the sun, it's possible for the felt temperature to increase by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. Children usually face more risks than adults as their ability to sweat is less. Additionally, their larger skin surface in relation to their petite bodies and higher heat output due to their activities increases their vulnerability.
Humidity
In September, the average relative humidity in Agat is 77%.Rainfall
September is the month with the most rainfall. Rain falls for 28.1 days and accumulates 10.28" (261mm) of precipitation.Daylight
In September, the average length of the day is 12h and 13min.On the first day of the month, sunrise is at 6:10 am and sunset at 6:32 pm. On the last day of September, in Agat, sunrise is at 6:10 am and sunset at 6:11 pm ChST.
Sunshine
In Agat, Guam, the average sunshine in September is 7.9h.UV index
September is the month with the lowest UV index, with an average maximum UV index of 6. A UV Index of 6 to 7 symbolizes a high threat to health from exposure to the Sun's UV rays for the average person.Note: The average daily UV index of 6 in September transforms into the following instructions:
Persist with precautions and heed sun safety advice. Prevention of sunburn is compulsory. Seek shade and limit direct Sun exposure between 10 a.m. and 4 p.m., when UV radiation is at its peak, but be aware that not all shade structures provide complete sun protection. Stay sun-safe with clothing that is both closely woven and worn loosely.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Agat, GU
- Average high temperature in September: 84.4°F
The warmest months (with the highest average high temperature) are July and August (84.7°F).
The month with the lowest average high temperature is February (81.7°F).
- Average low temperature in September: 82.8°F
The month with the highest average low temperature is June (83.3°F).
The coldest month (with the lowest average low temperature) is February (79.7°F).
Average pressure in September
Agat, GU
- Average pressure in September: 29.79"Hg
The month with the highest atmospheric pressure is February (29.88"Hg).
The months with the lowest atmospheric pressure are August, September and October (29.79"Hg).
Average wind speed in September
Agat, GU
- Average wind speed in September: 9.9mph
The windiest month (with the highest average wind speed) is February (16.3mph).
The calmest month (with the lowest average wind speed) is August (9.6mph).
Average humidity in September
Agat, GU
- Average humidity in September: 77%
The months with the highest relative humidity are January, March, April, May, October, November and December (78%).
The month with the lowest relative humidity is August (76%).
Average rainfall in September
Agat, GU
- Average rainfall in September: 10.28"
The wettest month (with the highest rainfall) is September (10.28").
The driest month (with the least rainfall) is March (1.81").
Average rainfall days in September
Agat, GU
- Average rainfall days in September: 28.1 days
The months with the highest number of rainy days are July and August (28.9 days).
The month with the least rainy days is February (17.5 days).
Average daylight in September /
Average sunshine in September
Agat, GU
- Average daylight in September: 12h and 12min
The month with the longest days is June (Average daylight: 12h and 54min).
The month with the shortest days is December (Average daylight: 11h and 24min).
- Average sunshine in September: 7h and 54min
The month with the most sunshine is June (Average sunshine: 10h and 36min).
The month with the least sunshine is November (Average sunshine: 6h and 18min).
Average sunshine days in September
Agat, GU
- Average sunshine days in September: 1.1 days
The month with the most sunshine days is March (6.6 days).
The month with the least sunshine days is September (1.1 days).
Average UV index in September
Agat, GU
- Average UV index in September: 6
The months with the highest UV index are January, February, March, April, May, June, July, August, October, November and December (UV index 7).
The month with the lowest UV index is September (UV index 6).
Average cloud cover in September
Agat, GU
- Average cloud cover in September: 45
The months with the most cloud cover are January, August and October (Cloud cover 46).
The months with the least cloud cover are May and June (Cloud cover 39).
Average visibility in September
Agat, GU
- 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).





