In East Timor, a small country located just south of the Equator, the climate is tropical, hot all year round, with a rainy season from December to March, and a dry season from June to September. The tropical rains fall in the form of showers or thunderstorms, maybe intense, but usually short-lived, so after a short time they give way to the sun, even in the rainy season.
The country includes the eastern part of the island of Timor, and the smaller islands of Atauro, to the north, and Jaco, to the east. There is also the exclave of Oecusse, in the western part of Timor, which for the rest belongs to Indonesia.
Temperatures are high and uniform throughout the year. They are slightly higher from October to May, and a bit lower from June to September, when highs are around 30 °C (86 °F). From September to November, and sometimes from mid-August, the hottest period of the year occurs. In the rainy season, high humidity makes the heat muggy.
Here are the average temperatures of the airport, located near the capital, Dili.
Dili - Average temperatures
Min (°C)242424232322222122242424
Max (°C)313031313130303030313231
Min (°F)757575737372727072757575
Max (°F)888688888886868686889088

The rains are not very abundant, and generally amount to 1,200/1,400 millimeters (47/55 inches) per year, but there are also some areas where rainfall drops below 1,000 mm (40 in), such as that of Dili, located on the north coast. Given that the rains are abundant only from December to March, and that the dry season is quite long, the landscape is not particularly verdant; actually, in some areas it is almost arid. Here is the average rainfall in Dili.
Dili - Average precipitation

The amount of sunshine in East Timor is good in the dry season, and remains acceptable even in the rainy season because, as we mentioned, the tropical rains, however intense, do not generally last long. On the contrary, in the interior the sky is more easily cloudy, especially on the mountain peaks.
Dili - Sunshine

From November to mid-May, but more often from January to mid-April, East Timor can be affected by tropical cyclones, which usually hit it in the early stages of their development, and therefore at a moderate intensity; however, they can bring an increase in wind and rainfall.
In the interior of East Timor, there is a mountain range. The highest peak is Mount Ramelau (or Tatamailau), 2,963 meters (9,721 feet) high. If you are planning some hiking at high altitudes, keep in mind that above 1,000 meters (3,300 feet) it's cool in the evening and at night, especially in the dry season, while above 2,000 meters (6,500 feet) it can get quite cold; in addition, at noon and in the afternoon the chance of thunderstorms in the highlands is higher than along the coasts.

Atauro Island

The sea in East Timor is warm enough to swim in throughout the year: the water temperature ranges from 29 °C (84 °F) between October and May, to 27 °C (81 °F) in July and August.
Dili - Sea temperature
Temp (°C)292929292928272728293030
Temp (°F)848484848482818182848686

Best Time

The best time to travel to East Timor and enjoy its beaches, is 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 mountainous areas.

What to pack

All year round, bring light clothes of natural fibers, a sun hat, a scarf for the breeze, a light sweatshirt for the evening. From November to March, a light raincoat or umbrella.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes.
When going mountain climbing, bring hiking shoes, a sweatshirt or sweater, a jacket, and a raincoat.