Climate The climate of Indonesia is almost everywhere equatorial, i.e., hot, humid and rainy throughout the year. In some areas, there is a dry season, marked, which is therefore the best period for a trip. As usually happens in hot countries, the rains occur in the form of downpours or thunderstorms, which sometimes can cause flooding.There are also mountains and volcanoes, often very high, where the temperature naturally decreases with altitude. Being that Indonesia is located near the Equator, the day lasts 12 hours throughout the year, and the sun sets quite soon. How- ever, the sun’s rays are very strong, especially in the mountains. The temperature is stable, with lows around 22/25 °C (72/77 °F) and highs around 30/32 °C (86/90 °F) all year round. The main difference is found in the rainfall, whose quantity and distribu- tion are due to the location in a hot and humid area, but also to the monsoon regime, and the impact that it has on the different areas. The northeast monsoon takes place from December to March, and the southwest monsoon from June to September. These winds have a different impact depending on the presence of mountains and on slope exposure. However, the rains do not always follow the same pattern from year to year, as we will see when dealing with El Niño. The climate is equatorial, with abundant rainfall throughout the year, in the following areas: the western coast and the western side of Sumatra, the southern side of western Java, almost all of Borneo (except the south- east) and much of Western New Guinea (formerly Irian Jaya). Here, it is difficult to find a best time to visit. The southern coast of Sumatra is very rainy. Here, around 4,000 millimeters (155 inches) of rain fall per year, and it is difficult to find an accept- able period. The worst period, however, is from October to De- cember, when rainfall amounts to more than 400 mm (16 in) per month. The only city of some importance in this area is Padang, which is relatively less rainy from June to August, although the decrease in precipitation does not occur every year. Off the south-west coast of Sumatra, we find the Mentawai Islands.