Bali
The dry season in Bali is from April to September. Expect bright, blue skies and plenty of sunshine. Within the dry season, the best months to visit Bali would be May, June and September. The crowd isn’t at its peak; the weather conditions are blissful. Bali experiences its wet season between October and March. The rainfall is usually brief, so you don’t have to worry about heavy downpours. The temperatures in Bali are consistent throughout the year, ranging between 26 to 29 degrees Celsius. The central regions of Bali and the mountains tend to experience colder temperatures and higher rainfall when compared to the coastal areas.Java
The best time to visit Java is during its dry season that starts in May and goes on till September. The days are dry, hot and sunny with daily temperatures around 28 to 30 degrees Celsius. The mountain regions such as Mt Bromo experience much colder temperatures, owing to the altitude. Java experiences its rainy season from November to March. The eastern parts of Java receive less rainfall than the western parts of Java. Expect frequent and intense showers that are bound to last for a couple of hours.Sumatra
Sumatra is a large island that is split by the equator. North Sumatra and Medan experience a somewhat tropical climate with chances of rainfall throughout the year. The most torrential rain in these regions is experienced between October and January. On the other hand, South Sumatra and Palembang have distinct wet and dry seasons. The dry season lasts from April to October and the wet season from November to March. The average temperatures range in between 27 to 28 degrees Celsius with some days reaching 34 degrees Celsius during the summer months.

The Moluccas
The best time to visit the Molucca islands is in the period from October to May. The central Molucca islands of Ambon and Seram experience entirely different weather patterns in comparison to the rest of Indonesia. These islands experience rainfall between June and September. The weather conditions in the remaining Molucca islands (Kei, Aru, Tidore and others) are similar to the rest of Indonesia and are best visited between May and September.

Kalimantan Island
The Kalimantan island experiences a light rainy season between March and May, a more substantial rainy season from November to January and the dry season from June to September. The southern parts of the island are relatively drier than the rainforest-covered northern regions.
The islands of Nusa Tenggara that include Lombok and the Gilis, Sumba and Flores experience their dry season from April to September and the wet season between October and March.

Peak Season
Indonesia experiences its peak tourist season from mid-June to mid-September and then again during Christmas and New Year’s. It is advised to make bookings well in advance if planning a trip during the peak season. The fares are at their peak during these months. Muslim festivals like Ramadan and Eid experience a surge in domestic tourism. The resorts are all completely booked and public transportation gets chaotic. Moreover, you will face increased fares for flights as well as accommodation.Shoulder Season
May, June and September constitute the shoulder season for tourism in Indonesia. It is a splendid time to plan a trip as the weather conditions are dry and sunny in most parts with the added advantage of fewer crowds and cheaper fares.Low Season
The wet season from October to April form the low season for tourism in Indonesia. One exception is the central islands of Molucca which experience warm, sunny weather during these months. You can expect to find good deals on accommodation and can also travel without any advance bookings.