Weather and climate in Surabaya (Indonesia)

The climate of Surabaya, Indonesia's second largest city, is tropical, hot all year round, with a rainy season from October to May and a dry season from June to September. The rains are abundant from December to March.
The city is located in the eastern part of the island of Java, on the north coast, at 7 degrees south latitude, and overlooks the Strait of Madura, which separates Java from the smaller island of Madura. South of Surabaya are volcanoes, including Penanggungan (the closest), 1,653 meters (5,423 feet) high, while further south are Arjuno, 3,319 meters (10,889 ft), and nearby Welirang, 3,156 meters (10,354 ft).
December to March is the period of the northwest monsoon, during which the rains are more frequent and abundant and the sky is more often cloudy.
June to September is the period of the southeast monsoon, which brings dry and relatively cool air. However, a thunderstorm can occasionally break out.
In September, temperatures begin to rise again slightly, and the period with the highest temperatures of the year begins, before the rainy season. The record heat is 36.7 °C (98 °F) and was recorded in October 2002. On the other hand, occasionally the temperature can drop slightly below 20 °C (68 °F) from June to September.
Since we are close to the Equator, the length of day and night is very similar throughout the year. The day lasts 11 hours 42 minutes on June 21, and 12 hours 33 minutes on December 21. The sun reaches the zenith at noon around October 11 and March 2.
Being close to the Equator and on the north side of Java, Surabaya is not affected by tropical cyclones. In the warm period of the southern hemisphere (between November and May, but more likely between December and mid-April), tropical cyclones can sometimes form on the Indian Ocean, which pass off the southern coast of Java, in the area of the Cocos Islands and of Christmas Island, and can bring heavy rain on the southern coast of Java.

Surabaya - Climate data

The average temperature of the coldest month (August) is of 26.9 °C (80.4 °F), that of the warmest month (November) is of 29.2 °C (84.6 °F). Here are the average temperatures.
Precipitation amounts to 1750 millimeters (68.9 inches) per year: it is therefore abundant. It ranges from 15 mm (0.6 in) in the driest months (July, August) to 325 mm (12.8 in) in the wettest one (January). Here is the average precipitation.
The sea temperature ranges from 27 °C (81 °F) in August to 29.5 °C (85 °F) in April, December. Here are the average sea temperatures.
There are on average around 2190 sunshine hours per year. Here are the average hours of sunshine per day.

Surabaya - Weather by month

Based on the period 1991-2020

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January is generally a very hot, muggy month. The average temperature is of 28.1 °C (83 °F), with a minimum of 24.2 °C (75.5 °F) and a maximum of 32.1 °C (89.8 °F).
On the coldest nights of the month, the temperature usually drops to around 22 °C (71.5 °F).
On the warmest days of the month, the temperature usually reaches around 34.5 °C (94 °F).
Precipitation amounts to 325 mm (12.8 in), distributed over 17 days.
The day lasts on average 12 hours and 30 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 36% of the time.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 29 °C (84.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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February is generally a very hot, muggy month. The average temperature is of 28.1 °C (83 °F), with a minimum of 24.1 °C (75.4 °F) and a maximum of 32.1 °C (89.7 °F).
On the coldest nights of the month, the temperature usually drops to around 22 °C (72 °F).
On the warmest days of the month, the temperature usually reaches around 34 °C (93.5 °F).
Precipitation amounts to 275 mm (10.8 in), distributed over 18 days.
The day lasts on average 12 hours and 20 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 36% of the time.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 29 °C (84 °F). Therefore, the sea is pleasantly warm and allows long swims.

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March is generally a very hot, muggy month. The average temperature is of 28.2 °C (83 °F), with a minimum of 24.3 °C (75.7 °F) and a maximum of 32.2 °C (89.9 °F).
On the coldest nights, the temperature usually drops to around 22 °C (71.5 °F).
On the warmest days, the temperature usually reaches around 34 °C (93 °F).
Precipitation amounts to 285 mm (11.2 in), distributed over 19 days.
The day lasts on average 12 hours and 5 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 38% of the time.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 29 °C (84.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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April is generally a very hot, muggy month. The average temperature is of 28.4 °C (83 °F), with a minimum of 24.7 °C (76.4 °F) and a maximum of 32.2 °C (89.9 °F).
On the coldest nights, the temperature usually drops to around 22.5 °C (73 °F).
On the warmest days, the temperature usually reaches around 33.5 °C (92.5 °F).
Precipitation amounts to 180 mm (7.1 in), distributed over 15 days.
The day lasts on average 11 hours and 55 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 44% of the time.
The average humidity is 78%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 29.5 °C (85 °F). Therefore, the sea is pleasantly warm and allows long swims.

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May is generally a very hot, muggy month. The average temperature is of 28.3 °C (83 °F), with a minimum of 24.5 °C (76.1 °F) and a maximum of 32.1 °C (89.7 °F).
On the coldest nights, the temperature usually drops to around 22 °C (71.5 °F).
On the warmest days, the temperature usually reaches around 33.5 °C (92.5 °F).
Precipitation amounts to 160 mm (6.3 in), distributed over 13 days.
The day lasts on average 11 hours and 50 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 76%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 29 °C (84.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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June is generally a very hot, muggy month. The average temperature is of 27.6 °C (82 °F), with a minimum of 23.7 °C (74.6 °F) and a maximum of 31.6 °C (88.9 °F).
On the coldest nights, the temperature usually drops to around 21.5 °C (70.5 °F).
On the warmest days, the temperature usually reaches around 33 °C (91.5 °F).
Precipitation amounts to 45 mm (1.8 in), distributed over 7 days.
The day lasts on average 11 hours and 40 minutes.
There are on average 6.5 hours of sunshine per day. So, the sun shines 57% of the time.
The average humidity is 74%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 28.5 °C (83.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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July is generally a warm to hot, muggy month. The average temperature is of 27.0 °C (81 °F), with a minimum of 22.6 °C (72.8 °F) and a maximum of 31.3 °C (88.3 °F).
On the coldest nights of the month, the temperature usually drops to around 20 °C (68 °F).
On the warmest days of the month, the temperature usually reaches around 32.5 °C (91 °F).
Precipitation amounts to 15 mm (0.6 in), distributed over 5 days.
The day lasts on average 11 hours and 40 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 62% of the time.
The average humidity is 72%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 27.5 °C (81.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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August, the least warm month of the year, is generally a warm to hot month. The average temperature is of 26.9 °C (80 °F), with a minimum of 22.3 °C (72.1 °F) and a maximum of 31.5 °C (88.7 °F).
On the coldest nights of the month, the temperature usually drops to around 20 °C (68 °F).
On the warmest days of the month, the temperature usually reaches around 33 °C (91 °F).
Precipitation amounts to 15 mm (0.6 in), distributed over 3 days.
The day lasts on average 11 hours and 55 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 66% of the time.
The average humidity is 69%.
The average wind speed is 12 kph (7 mph).
The average sea temperature is of 27 °C (81 °F). Therefore, the sea is pleasantly warm and allows long swims.

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September is generally a very hot month. The average temperature is of 27.7 °C (82 °F), with a minimum of 22.8 °C (73 °F) and a maximum of 32.6 °C (90.7 °F).
On the coldest nights, the temperature usually drops to around 20.5 °C (69 °F).
On the warmest days, the temperature usually reaches around 34 °C (93 °F).
Precipitation amounts to 20 mm (0.8 in), distributed over 4 days.
The day lasts on average 12 hours and 5 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 63% of the time.
The average humidity is 66%.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 27.5 °C (81 °F). Therefore, the sea is pleasantly warm and allows long swims.

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October is generally a very hot month. The average temperature is of 28.9 °C (84 °F), with a minimum of 24.1 °C (75.5 °F) and a maximum of 33.6 °C (92.6 °F).
On the coldest nights, the temperature usually drops to around 22 °C (71.5 °F).
On the warmest days, the temperature usually reaches around 35 °C (95.5 °F).
Precipitation amounts to 100 mm (3.9 in), distributed over 11 days.
The day lasts on average 12 hours and 20 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 58% of the time.
The average humidity is 67%.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 28 °C (83 °F). Therefore, the sea is pleasantly warm and allows long swims.

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November, the hottest month of the year, is generally a very hot, muggy month. The average temperature is of 29.2 °C (85 °F), with a minimum of 24.9 °C (76.7 °F) and a maximum of 33.5 °C (92.4 °F).
On the coldest nights, the temperature usually drops to around 22.5 °C (73 °F).
On the warmest days, the temperature usually reaches around 35 °C (95 °F).
Precipitation amounts to 105 mm (4.1 in), distributed over 12 days.
The day lasts on average 12 hours and 25 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 49% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 9 kph (5 mph).
The average sea temperature is of 29 °C (84.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

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December, the hottest month of the year, is generally a very hot, muggy month. The average temperature is of 28.5 °C (83 °F), with a minimum of 24.4 °C (76 °F) and a maximum of 32.6 °C (90.7 °F).
On the coldest nights of the month, the temperature usually drops to around 23 °C (73 °F).
On the warmest days of the month, the temperature usually reaches around 35 °C (95 °F).
Precipitation amounts to 220 mm (8.7 in), distributed over 23 days.
The day lasts on average 12 hours and 30 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 36% of the time.
The average humidity is 78%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 29.5 °C (84.5 °F). Therefore, the sea is pleasantly warm and allows long swims.