In Komodo, and on the nearby islands that make up the national park of the same name (Padar, Rinca, plus other smaller islands), the climate is tropical, hot all year round, with a muggy and rainy season from December to March, and a dry season from June to September. In the rainy season the sun shines for a few hours a day, in fact it usually rains a couple of hours in the morning and a couple of hours in the afternoon.
Temperatures are high and quite uniform throughout the year. The least hot period is from June to August. From September to November, and sometimes from mid-August, the hottest period of the year occurs, when the temperature can reach 35/37 °C (95/99 °F). In the rainy season, on the other hand, high relative humidity makes the heat muggy.
Here are the average temperatures.
Komodo - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)242424232222212122242524
Max (°C)323232333332323334353533
Min (°F)757575737272707072757775
Max (°F)909090919190909193959591

The rains are not particularly abundant, and given 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 of Waingapu, on the nearby island of Sumba.
Waingapu - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)17016014570352510551040135810
Prec.(in)6.76.35.72.81.410.40.20.20.41.65.331.9
Days131311964311261180

In Komodo there's plenty of sunshine in the dry season, while in the rainy season the sun shines for a few hours a day, between a rainshower and the other.
Komodo - Sunshine
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Hours667888899986

Komodo

The sea in Komodo is warm enough to swim in throughout the year: the water temperature goes from 29 °C (84 °F) from November to May, to 27 °C (81 °F) in July, August and September.
Komodo - Sea temperature
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Temp (°C)292929292928272727282930
Temp (°F)848484848482818181828486

From November to mid-May, but more often from January to mid-April, Komodo can be affected by tropical cyclones, which are formed on the sea of Timor, and then move south-westard, between the Sunda Islands and Australia.

When to go


The best time to travel to Komodo 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 the rains have not started yet, but it starts to get very hot.

What to pack


All year round, light clothes, of natural fibres, a sun hat, a scarf for the breeze, a light sweatshirt for the evening. From December to March, a light raincoat or umbrella.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes.