December weather forecastUmatac, GU
December
Weather in December
Rounding off the year, December in Umatac, Guam features a further decline in rainfall to 2.99" (76mm), a drop from November's already reduced precipitation. This downward trend marks the cessation of the rainy season. Despite a decrease in glory, the weather radiates a gentle elegance with its subtropical warmth and winds. Sunshine hours narrow marginally, allowing for comfortable daylight use. Notwithstanding the cooler season, the UV index remains consistent, advocating for year-round sun protection practices.Temperature
The advent of December presents an average high-temperature of a still moderately hot 83.5°F (28.6°C), maintaining a close correlation with the preceding month. Umatac reports an average low-temperature of 82°F (27.8°C) during the subtly cooler December nights.Heat index
The heat index value for December is estimated at a tropical 91.4°F (33°C). Exercise heightened safety, heat cramps and heat exhaustion are probable. Persistent activity may provoke heatstroke.Factoring in the heat index, values are geared towards shaded areas with light breezes. Heat index values can rise by 15 Fahrenheit (8 Celsius) degrees when in direct sunlight.
Note: The heat index, also known as 'felt air temperature' or 'real feel', is a numerical representation of warmth when taking temperature and moisture levels into account. The effect is personal, with varied weather perceptions among individuals due to differences in body mass, stature, and physical activity. You should know that direct sun exposure can heighten weather effects, potentially elevating the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values hold particular importance for children. Young children typically face greater hazards than adults because they do not sweat as much. Their larger skin surface in comparison to their little bodies and the high heat production from their active nature compounds their vulnerability.
Humidity
January, March through May, October through December, with an average relative humidity of 78%, are the most humid months.Rainfall
In December, the rain falls for 22.8 days. Throughout December, 2.99" (76mm) of precipitation is accumulated. In Umatac, during the entire year, the rain falls for 288.5 days and collects up to 60.08" (1526mm) of precipitation.Daylight
December has the shortest days of the year, with an average of 11h and 24min of daylight.On the first day of December in Umatac, sunrise is at 6:28 am and sunset at 5:52 pm. On the last day of the month, sunrise is at 6:43 am and sunset at 6:05 pm ChST.
Sunshine
In Umatac, the average sunshine in December is 6.5h.UV index
January through August, October through December, with an average maximum UV index of 7, are months with the highest UV index. A UV Index of 6 to 7 symbolizes a high health vulnerability from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The maximum UV index of 7 during December translates into these guidelines:
Sidestep overexposure. Individuals with fair complexions risk burning in fewer than 20 minutes. Avoid direct exposure to the Sun between 10 a.m. and 4 p.m., the peak period for UV radiation, noting that objects like parasols or canopies might not offer complete sun protection. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Umatac, GU
- Average high temperature in December: 83.5°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 December: 82°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 December
Umatac, GU
- Average pressure in December: 29.83"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 December
Umatac, GU
- Average wind speed in December: 15.7mph
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 December
Umatac, GU
- Average humidity in December: 78%
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 December
Umatac, GU
- Average rainfall in December: 2.99"
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 December
Umatac, GU
- Average rainfall days in December: 22.8 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 December /
Average sunshine in December
Umatac, GU
- Average daylight in December: 11h and 24min
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 December: 6h and 30min
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 December
Umatac, GU
- Average sunshine days in December: 4.7 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 December
Umatac, GU
- Average UV index in December: 7
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 December
Umatac, GU
- Average cloud cover in December: 44
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 December
Umatac, GU
- Average visibility in December: 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).
