Sumatra Climate and Weather
The Indonesian climate is tropical. The warm waters of the ocean surrounding the archipelago ensure fairly constant temperatures on land and there is little seasonal variation. There is also very little difference in daylight hours from season to season.
Sumatra's weather is typical for Indonesia, but temperatures can often be lower than expected in the highlands. This slightly cooler and less humid highland climate can be a great relief and is good for hiking and other adventurous activities. The average daytime highs in Sumatra range from 72F to 86F (22C to 30C) while the rainfall differs from region to region and humidity levels are high in the lowlands. There are two main seasons: the dry season runs from February to August; and the wet season from September to January.
The climate of Indonesia is dominated by heavy monsoon rains, which generally occur between October and April, often causing damage and making local travel difficult (the rainy season is also the worst time for some mosquito-borne diseases). The best time of year to visit Sumatra is any time during the dry season.