December weather forecast
Umatac, GU

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.