We’re big fans of ‘shoulder season’ across Asia and September in Indonesia is just that: there’s a high chance of great weather still and far lower visitors numbers are expected than the past few peak season months. The western and central islands such as Bali, Lombok and Java are still expecting good weather and in the eastern islands things are improving fast, especially towards the end of the month.
NB: the westernmost point of Indonesia is a full 3200 miles from the eastern most tip, so it should come as no surprise that summarising the weather is not straightforward. The tables above split the ‘country’ (made up of 17,508 islands) into two regions - the western & central islands and the eastern islands (that sit to the east of the Wallace Line), however we encourage you to read the more detailed summaries below as there can be significant variations in conditions between the islands within each group.
Visitor numbers are still high in early September however they start to decline as the month drawers to an end, which means September is a great time to visit Java if you wish to take advantage of peak weather conditions without peak crowds at the popular tourist spots of Yogyakarta and Borobudur. Days are still hot, with maximum highs of 33-34°C not uncommon (especially in Jakarta), although humidity levels are relatively low. September is one of the hottest, driest months of the year in Java.
As dry season comes to an end in Bali, September is still a predominantly dry month with plenty of sunshine and blue skies, and temperatures still a very warm 27°C, although rainfall can be expected towards the end of the month. Visitor numbers tend to drop off during September, meaning less crowds at temples and on the popular south coast beaches of Jimbaran, Seminyak and Sanur. In our opinion, September is one of the best months to be visiting Bali.
You can expect another dry month on Lombok & the Gili Islands, Flores & Sumba in September, with plenty of sunshine. Temperatures start to climb towards the end of the month and can reach 31°C on occasion. Favourable diving and snorkelling conditions continue off the coast of Lombok, the Gili Islands and in the Komodo National Park, with water temperatures around 27°C.
September is another popular month to be visiting the Nusa Tenggara islands.
Weather conditions throughout Kalimantan in September are much the same as August: expect minimal rainfall, dry & sunny days and balmy temperatures which can reach 32°C. As the dry weather continues, it's a good time of year to spot orang-utans in Tanjung Puting National Park.
September is one of the driest months of the year in Sumatra, although the odd intense downpour should still be expected in Medan and North Sumatra, especially towards the tail end of the month. Average temperatures remain around 28°C. Visitor numbers start to decline towards the end of September, making it a great time to visit Sumatra if you wish to enjoy peak conditions without peak crowds.
Sunny, dry days continue across southern Sulawesi, with the chance of showers in Manado and the northern regions. Humidity levels remain comfortable, although temperatures are gradually rising and the mercury can regularly hit 33°C & 34°C in September. Minimal rainfall and hot, sunny weather means September is a good month to visit Sulawesi.
September is shoulder season across the Molucca Islands. The central islands of Ambon and Seram typically experience less rainfall than previous months. The high winds that have plagued the Banda Islands in previous months have now disappeared, making September a good time of year to visit the Banda Islands. September is an excellent time of year for spotting the Greater Birds of Paradise on the island of Aru.
September is the final month of the southeast monsoon in Raja Ampat. Strong winds and intense downpours can be expected at the beginning of September but will tail off by the end of the month. Wamena and the Baliem Valley are drier, although occasional showers can be expected, with average daily temperatures hovering around 23°C in the highlands and 30°C at sea level.