There isn't any time of year that's bad to visit Indonesia but the weather systems do vary significantly from place to place. Knowing the climate, sometimes, can be essential to picking the right place to go.
Overall, climate across Indonesia is driest and least humid from about June to August, when most tourists travel to Bali. Shoulder periods (Apr-May and Sep-Oct) are popular for escaping crowds.
Annual rainfall decreases further southeast. The west (Sumatra & Java) are more influenced by monsoon than the east (Lesser Sundas, Bali) where it tends to be quite dry, even in the ‘wet’ season. The closer you go to the equator (North Sulawesi, Sumatra, Kalimantan), the less distinction between the seasons and the higher the overall rainfall.
- Indonesia is not in the typhoon belt, so cyclones are exceedingly rare!
Temperature and rainfall also varies significantly with altitude.
- Rainfall increases with altitude, so climbing volcanoes is best in the dry.
- Similarly, the West Papua highlands can have 900mm of rain in the wet (which translates into heavy snowfall in the highest elevations).
- Average temperatures fall by between 6-10 degrees celsius for every 1,000m elevation.
This means that even in the warmest and most humid islands, such as Sumatra, a lot of highland experiences are comfortable and even during the most humid months, travel is possible and comfortable if you choose the right destination.
Temperatures are consistently in the high 20s to low-30s degrees celsius. Rainfall is most frequent from October to March, except east of the Moluccas, including West Papua where it’s opposite, from about mid-June to September.
A few simple rules
- Temperatures are relatively consistent year-round.
- The closer you go to the equator, the wetter it gets and the less distinction between the wet and dry seasons (N KALIMANTAN, N SULAWESI, PAPUA).
- The further south-east you go, the drier it gets (EAST JAVA, BALI, KOMODO, FLORES).
- The further south-east you go, the later the dry season gets
- The wet season is the opposite in RAJA AMPAT (but WEST PAPUA highlands are very wet in the warmest months).
- The higher in altitude you go, the wetter and cooler it gets.