All of Indonesia has a tropical climate. However, in general the country is divided into wet and dry season. Wet season consist of heavy rain and occasional winds. Although it is seemingly possible to walk in the tropical rain, it’s another matter to be exposed to humidity. Staying dry is still important.
During the dry season, the sun is hot the air humid. Sunblock is necessary as sunlight is abundant, as well as aftersun gel to cool off. Micro climate differs which could be impacted from elevation and distance from the coast.
Best time to travel
Consisting of forest, rich in mountains and highlands, the west of Indonesia is travel friendly throughout the year.
Most popular time to travel is May to September.
From November to March there can be heavy rain. Traveling is still possible during the wet season, but clothes can get wet and views might be hazy. Also note that rain in the tropics is very humid.
Crossing to the east, Bali-Lombok being a transitional area, the weather is drier compared to that in Java. It’s optimal for traveling during April to November. The rest of the year is possible to travel with the occasional heavy winds, challenging for sailing and sea activities. Sail warnings are fairly strict although the boat people can determine whether it’s safe to sail or not.
There are some regional exceptions. In Northern Sumatra it can rain from October to January, in the south between November and February. Sulawesi, with its unusual shape, also experiences slightly different weather patterns and rainfall can be expected in the northern regions of the island during June and July.
Microclimate involves elevated areas which can reach around 0 degrees such as in Dieng highlands and Semeru Mountain (Java) , you might need winter clothes.