The climate in Indonesia

Climate zone: tropics

High humidity and hot temperatures make the weather in Indonesia pleasant at times but also tropical humid. It is warm to hot all year round, inviting bathing at average water temperatures of 28 degrees. The warmest and at the same time rainiest island group is Java. The coldest is Moluccas. Due to less rain, the best time for traveling is from August to September. Most precipitation falls from December to January.

Temperature records of the last 74 years

The hottest temperature measured from 1949 to January 2023 was reported by the Maumere weather station. In September 2001, the record temperature of 43.1 °C was reported here. The hottest summer from July to September, based on all 127 weather stations in Indonesia below 850 meters altitude, was recorded in 2016 with an average temperature of 27.4 °C. This average temperature will normally be measured every four to six hours, thus also including the nights. Normally, this value is 26.9 degrees Celsius. The average maximum daily temperature at that time was 31.9 °C.

The coldest day in these 74 years was reported by the Fak Fak weather station. Here the temperature dropped to zero °C in June 2009. Fak Fak lies at an altitude of 130 meters above sea level. The coldest winter (January to March) was in 1963 with an average temperature of 25.7 °C. In Indonesia, it is usual to have about 1.3 degrees more at 27.1 °C for this three-month period.

The most precipitation fell in February 1953. With 78.6 mm per day, the Makassar Airport weather station recorded the highest monthly average of the last 74 years. Incidentally, the region with the most rainfall for the whole year is around Tanah Merah. The driest region is near Palu Airport.

Long-term development of temperatures from 2000 - 2022

In contrast to single record values, long-term development cannot simply be brought about by all weather stations in the country. Both the number and the locations are constantly changing. An average value would give a distorted result. If several measuring stations in particularly cold mountain or coastal regions are added in one year, the average would decrease as a result of this alone. If a station fails during the summer or winter months, it does not provide any values and distorts the average again. The subsequent long-term development was therefore reduced to only 4 measuring points in order to have comparable data over as long a period as possible.

In the years 2000 to 2022, there were only these 4 weather stations in the whole country, which reported continuous temperature values (Medan, Sibolga, Denpasar, Rengat). From these weather reports, we have created a long-term development that shows the monthly average temperatures. The hottest month in this entire period was April 2016 at 28.5 °C. September 2006 was the coldest month with an average temperature of 26.1 °C.

The average annual temperature was about 26.9 °C in the years after 2000 and about 27.2 °C in the last years before 2022. So over the past 23 years, it has only increased by a minimal 0.3 °C. This trend only applies to the selected 4 weather stations in Indonesia. A considerably more comprehensive evaluation of global warming has been provided separately.

Data basis and methodology

The data from the individual measuring stations are based on the archives of the German Weather Service, individual values averaged and supplemented by own elements. In order to determine a representative national average, average values were first calculated for each part of the country, which were then summarized at the national level. Thus, if a disproportionate number of weather stations are located in a small area, their number does not affect the national average. There are 128 stations in Indonesia itself. In 5 cases, neighboring but nearby weather stations were also used to obtain more accurate values.