December weather forecast
Surabaya, Indonesia

December in Surabaya heralds a robust wet season characterized by frequent rainfall and increased humidity. Despite this trend, the temperature remains pleasantly warm, favoring holiday festivities. The sea temperature rises to its highest annual peak of 30.2°C (86.4°F), perfect for those willing to brave the rainfall for marine adventures. Sightseers should anticipate reduced sunshine hours, which are expected during the wet season. The moderate wind speed experienced in this month brings the year's weather circle to a close, ready to usher in the New Year with a fresh slate of weather patterns.

Temperature

The shift into December in Surabaya uncovers an average high-temperature of a still tropical 31.2°C (88.2°F), subtly different from the previous month. Surabaya's average temperature during the nights of December is recorded at a moderately hot 26.3°C (79.3°F).

Heat index

For most parts of December, the heat index is evaluated at a fiery hot 39°C (102.2°F). Emphasize additional safety, risk of heat cramps and heat exhaustion is high. Continuous activity might result in heatstroke.
Consider that heat index readings are for situations in the shade and light wind. Heat index values may be hiked up by 15 Fahrenheit (8 Celsius) degrees under direct sunshine.
Note: The heat index, also known as 'feels like' or 'felt air temperature', arises from combining readings of air temperature and relative moisture content. The influence of weather is personal, differing among a variety of individuals based on differences in body mass, stature, and the level of physical activity. In the direct sunlight, the weather's impact can be amplified, possibly boosting the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical to babies and toddlers. Young ones often disregard the necessity to rest and hydrate. Thirst usually indicates advanced dehydration - hence, it is key to stay hydrated, particularly during ongoing physical activities.
In response to overheating, the human body perspires to cool down, mainly through the evaporation of sweat. With higher relative humidity, the rate of evaporation is reduced, resulting in increased heat retention in the body compared to drier air. As the body accumulates more heat than it can release, body temperature goes up, increasing the risk of heat-related health issues.

Humidity

The average relative humidity in December in Surabaya is 74%.

Rainfall

In Surabaya, Indonesia, during December, the rain falls for 24.7 days and regularly aggregates up to 102mm (4.02") of precipitation. Throughout the year, in Surabaya, there are 187.8 rainfall days, and 839mm (33.03") of precipitation is accumulated.

Sea temperature

With an average sea temperature of 30.2°C (86.4°F), December is the month with the warmest seawater.
Note: The cool, rejuvenating sensation of water can be lacking when temperatures are beyond 30°C (86°F).

Daylight

With an average of 12h and 30min of daylight, December has the longest days of the year.
On the first day of December, sunrise is at 05:02 and sunset at 17:33. On the last day of the month, sunrise is at 05:15 and sunset at 17:48 WIB.

Sunshine

In Surabaya, the average sunshine in December is 8.6h.

UV index

The months with the highest UV index in Surabaya are January through December, with an average maximum UV index of 7. The months with the lowest UV index are January through December, with an average maximum UV index of 7. A UV Index of 6 to 7 symbolizes a high threat to health from unprotected exposure to Sun's UV rays for the average person.
Note: The maximum daily UV index of 7 during December translates into the following directions:
Refrain from overexposure. Fair-skinned individuals could burn in under 20 minutes. 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. Outfit yourself in sun-safe attire, like long sleeves, pants, a hat, and UV-blocking sunglasses. Stay cautious! Sand and water reflections increase UV radiation potency.