December weather forecast
Surabaya, Indonesia

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The skyscrapers making the cityscape of Surabaya in East Java, Indonesia
The skyscrapers making the cityscape of Surabaya in East Java, Indonesia

Weather in December

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.

Frequently asked questions

How hot is December in Surabaya?

Surabaya in December has an average high-temperature of 31.2°C (88.2°F) and an average low-temperature of 26.3°C (79.3°F). The average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which factors the actual air temperature with the relative humidity, in December is evaluated at 39°C (102.2°F).

What is the average humidity in December in Surabaya?

In December, the average relative humidity is 74%.

How many days does it rain in December in Surabaya?

In Surabaya, in December, it is raining for 24.7 days, with typically 102mm (4.02") of accumulated precipitation.

What month is the sea warmest in Surabaya?

December is the month with the warmest seawater in Surabaya, with an average sea temperature of 30.2°C (86.4°F).

What is the sea temperature in December in Surabaya?

In Surabaya, Indonesia, in December, the average water temperature is 30.2°C (86.4°F). For swimming, other intense water activities, temperature above 30°C (86°F) is arguably unpleasant, as the water cooling effect is missing.

When are the longest days in Surabaya?

With an average of 12h and 30min of daylight, December has the longest days of the year.

How many hours of daylight does Surabaya have in December?

The average day length in December in Surabaya is 12h and 32min.

When are sunrise and sunset in December in Surabaya?

In December, on the first day of the month, sunrise is at 05:02 and sunset at 17:33. On the last day of the month, in Surabaya, sunrise is at 05:15 and sunset at 17:48 WIB.

How many hours of sunshine does Surabaya have in December?

The average sunshine duration in December is 8.6h.

When is the highest UV index in Surabaya?

The months with the highest UV index in Surabaya, Indonesia, are January through December, with an average maximum UV index of 7.

What is the month with the lowest UV index in Surabaya?

The months with the lowest UV index in Surabaya, Indonesia, are January through December, with an average maximum UV index of 7.

How high is the UV index in December in Surabaya?

The average daily maximum UV index in December in Surabaya, Indonesia, is 7. A UV Index estimate of 6 to 7 represents a high health vulnerability from unsafe exposure to Sun's UV rays.

Average temperature in December
Surabaya, Indonesia

Average temperature in December - Surabaya, Indonesia
  • Average high temperature in December: 31.2°C

The warmest month (with the highest average high temperature) is October (32.9°C).
The months with the lowest average high temperature are January, February and July (30.1°C).

  • Average low temperature in December: 26.3°C

The month with the highest average low temperature is November (26.5°C).
The coldest month (with the lowest average low temperature) is August (24.2°C).

Average pressure in December
Surabaya, Indonesia

Average pressure in December - Surabaya, Indonesia
  • Average pressure in December: 1008.7mbar

The month with the highest atmospheric pressure is August (1011.4mbar).
The month with the lowest atmospheric pressure is December (1008.7mbar).

Average wind speed in December
Surabaya, Indonesia

Average wind speed in December - Surabaya, Indonesia
  • Average wind speed in December: 7km/h

The windiest month (with the highest average wind speed) is August (9.9km/h).
The calmest month (with the lowest average wind speed) is April (6.3km/h).

Average humidity in December
Surabaya, Indonesia

Average humidity in December - Surabaya, Indonesia
  • Average humidity in December: 74%

The month with the highest relative humidity is February (79%).
The month with the lowest relative humidity is October (63%).

Average rainfall in December
Surabaya, Indonesia

Average rainfall in December - Surabaya, Indonesia
  • Average rainfall in December: 102mm

The wettest month (with the highest rainfall) is February (179mm).
The driest month (with the least rainfall) is August (4mm).

Average rainfall days in December
Surabaya, Indonesia

Average rainfall days in December - Surabaya, Indonesia
  • Average rainfall days in December: 24.7 days

The month with the highest number of rainy days is January (27 days).
The month with the least rainy days is August (3.7 days).

Average sea temperature in December
Surabaya, Indonesia

Average sea temperature in December - Surabaya, Indonesia
  • Average sea temperature in December: 30.2°C

The best month for swimming (with the highest average sea temperature) is December (30.2°C).
The coldest month (with the lowest average sea temperature) is August (27.8°C).

Average daylight in December /
Average sunshine in December
Surabaya, Indonesia

Average daylight in December / Average sunshine in December - Surabaya, Indonesia
  • Average daylight in December: 12h and 3min

The month with the longest days is December (Average daylight: 12h and 30min).
The month with the shortest days is June (Average daylight: 11h and 42min).

  • Average sunshine in December: 8h and 4min

The months with the most sunshine are August, September and October (Average sunshine: 9h and 54min).
The month with the least sunshine is January (Average sunshine: 8h and 6min).

Average sunshine days in December
Surabaya, Indonesia

Average sunshine days in December - Surabaya, Indonesia
  • Average sunshine days in December: 5.9 days

The month with the most sunshine days is August (26 days).
The month with the least sunshine days is February (2.8 days).

Average UV index in December
Surabaya, Indonesia

Average UV index in December - Surabaya, Indonesia
  • Average UV index in December: 7

The months with the highest UV index are January, February, March, April, May, June, July, August, September, October, November and December (UV index 7).
The months with the lowest UV index are January, February, March, April, May, June, July, August, September, October, November and December (UV index 7).

Average cloud cover in December
Surabaya, Indonesia

Average cloud cover in December - Surabaya, Indonesia
  • Average cloud cover in December: 38

The month with the most cloud cover is January (Cloud cover 44).
The month with the least cloud cover is August (Cloud cover 11).

Average visibility in December
Surabaya, Indonesia

Average visibility in December - Surabaya, Indonesia
  • Average visibility in December: 10km

The months with the highest visibility are March, April, May, June, July, August, September, October, November and December (10km).
The months with the lowest visibility are January and February (9km).

Surabaya, Indonesia

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