In Sumba, an Indonesian island belonging to the group of the Lesser Sunda Islands, the climate is
tropical, hot all year round, with a rainy season from December to March and a dry season from June to October.
Temperatures are high and uniform throughout the year. They are slightly higher from October to May and a bit lower from June to August, when the southeast monsoon blows and the minimum temperature can drop to 18/19 °C (64/66 °F). In August 2012 it dropped to 15.5 °C (60 °F). On the other hand, the hottest days of the year, with highs about 35/36 °C (95/97 °F), are often recorded in October and November, before the rainy season. In the latter, high humidity makes the heat muggy.
Here are the average temperatures at the airport, located on the north coast, near Waingapu.
Waingapu - Average temperatures (1991-2020) | Month | Min (°C) | Max (°C) | Mean (°C) | Min (°F) | Max (°F) | Mean (°F) |
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| January | 24 | 32 | 28.1 | 75 | 90 | 82.5 |
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| February | 24 | 32 | 27.8 | 75 | 89 | 82.1 |
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| March | 24 | 32 | 27.9 | 75 | 90 | 82.3 |
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| April | 23 | 32 | 27.8 | 74 | 90 | 82 |
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| May | 23 | 32 | 27.1 | 73 | 89 | 80.9 |
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| June | 22 | 31 | 26.3 | 71 | 88 | 79.3 |
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| July | 21 | 31 | 25.8 | 69 | 88 | 78.4 |
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| August | 20 | 31 | 25.7 | 68 | 88 | 78.3 |
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| September | 21 | 32 | 26.7 | 70 | 90 | 80.1 |
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| October | 23 | 33 | 28.2 | 74 | 92 | 82.7 |
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| November | 24 | 33 | 28.8 | 76 | 92 | 83.9 |
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| December | 25 | 33 | 28.6 | 76 | 91 | 83.4 |
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| Year | 22.8 | 32 | 27.35 | 73 | 89.7 | 81 |
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is not very abundant, especially along the north coast and at low altitude, where it drops below 1,000 millimeters (40 inches) per year. Given that the rains are only abundant from December to March, and that the dry season is quite long, the landscape is not particularly verdant, in fact, in some areas, it is almost arid. Here is the average rainfall in Waingapu.
Waingapu - Average precipitation| Month | Millimeters | Inches | Days |
|---|
| January | 170 | 6.7 | 13 |
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| February | 160 | 6.3 | 13 |
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| March | 145 | 5.7 | 11 |
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| April | 70 | 2.8 | 9 |
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| May | 35 | 1.4 | 6 |
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| June | 25 | 1 | 4 |
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| July | 10 | 0.4 | 3 |
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| August | 5 | 0.2 | 1 |
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| September | 5 | 0.2 | 1 |
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| October | 10 | 0.4 | 2 |
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| November | 40 | 1.6 | 6 |
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| December | 135 | 5.3 | 11 |
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| Year | 810 | 31.9 | 80 |
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In the interior of the island, there are hills that reach about 1,000 meters (3,300 feet), where the rains are a little more abundant. In some areas, there are forests and waterfalls (which, however, often dry up in the dry season).
In Sumba, there's plenty of
sunshine in the dry season, while in the rainy season, the sun shines for a few hours a day, between one rain shower and another. Here are the average sunshine hours per day.
Waingapu - Sunshine hours| Month | Average | Total |
|---|
January | 6.5 | 195 | February | 6 | 175 | March | 7 | 220 | April | 8.5 | 260 | May | 9 | 280 | June | 9 | 265 | July | 9 | 280 | August | 9.5 | 295 | September | 9.5 | 290 | October | 9.5 | 300 | November | 8.5 | 255 | December | 7 | 220 | Year | 8.3 | 3040 |
From November to mid-May, but more often from January to mid-April, Sumba can be affected by
tropical cyclones, which are formed on the Timor Sea, and then move south-westard, between the Sunda Islands and Australia.
Together with Timor and the smaller islands of Savu and Rote, Sumba is located further south than the other Sunda islands, so it is hit a little more often by tropical cyclones. For example, it was hit by Cyclone Inigo in early April 2003 and by Cyclone Seroja in early April 2021.
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The sea in Sumba is warm enough to swim in throughout the year: the water temperature ranges from 26/27 °C (79/81 °F) between July and September to 29 °C (84 °F) between November and April. Here are the average sea temperatures.
Waingapu - Sea temperature| Month | Celsius (°C) | Fahrenheit (°F) |
|---|
January | 29.5 | 85 | February | 29 | 85 | March | 29.5 | 85 | April | 29.5 | 85 | May | 28.5 | 83 | June | 27.5 | 82 | July | 27 | 80 | August | 26.5 | 80 | September | 27 | 81 | October | 28 | 83 | November | 29.5 | 85 | December | 29.5 | 85 | Year | 28.4 | 83.1 |
Best Time
The best time to travel to Sumba and enjoy its beaches goes from
June to August: the sun shines, the heat is not too intense, and in any case, it's tempered by the breeze; there are just some short downpours or thunderstorms every now and then. In September, it is often very hot. At the end of September or in October, the rains begin to increase in inland and hilly areas.
What to pack
All year round, bring light clothes of natural fibers, a sun hat, a scarf for the breeze, and a light sweatshirt for the evening (especially from June to September). From December to March, you can add a light raincoat or umbrella.