Although the calendar has marked the arrival of the dry season, several regions across Indonesia continue to experience frequent rainfall.
This phenomenon is not without explanation. The Meteorology, Climatology and Geophysics Agency (BMKG) has confirmed that Indonesia is currently experiencing a wet drought.
BMKG Deputy for Meteorology, Guswanto, explained that wet drought is a condition in which the dry season is still marked by significant rainfall.
Usually, the dry season is associated with hot weather and clear skies. However, during a wet drought, air humidity remains high, allowing for frequent rain.
“Wet drought is an unusual phenomenon that can be caused by various factors, including climate change and unstable weather patterns,” he said as reported by Kompas.com, Wednesday, 14 May 2025.
Contributing Atmospheric Factors
The BMKG identified several atmospheric dynamics that have contributed to the emergence of this year’s wet drought.
These include the presence of cyclonic circulation in the Indonesian region, the Madden-Julian Oscillation (MJO) phenomenon, and atmospheric waves such as Kelvin waves, Equatorial Rossby, and Low Frequency waves.
These conditions encourage the continual formation of rain clouds, leading to sustained rainfall in certain areas, despite it being the dry season.
Guswanto clarified that the wet drought phenomenon is not uniformly experienced throughout Indonesia.
“Especially areas with monsoonal rain patterns, namely in Java, Bali and Nusa Tenggara,” he said.
Regions with monsoonal rain patterns typically experience two distinct seasons: the rainy season and the dry season, each with a single peak, known as a unimodal pattern.
However, this year, that pattern is disrupted due to rainfall during the supposed dry season.
The BMKG estimates that the wet drought conditions will continue until August 2025.
Following that, Indonesia is predicted to enter a transition period from September to November, ahead of the return of the rainy season, which is expected from December 2025 to February 2026.
What Is Wet Drought?
Wet drought is an unusual meteorological condition in which rain continues to fall with considerable intensity even though the region is entering the dry season. Traditionally, the dry season is characterised by hot temperatures, minimal clouds, and clear skies. However, in cases of wet drought, air humidity remains high, allowing rainfall to persist.
BMKG Deputy for Meteorology, Guswanto, explained that this phenomenon may arise due to various factors, including climate change and unstable weather patterns.
Beyond this, several atmospheric dynamics have been identified as contributing to wet droughts, such as cyclonic circulation, the Madden-Julian Oscillation (MJO), and waves like Kelvin, Equatorial Rossby, and Low Frequency.
Globally, this condition is also known as wet drought, wherein an area receives rainfall that appears normal or above average, yet the availability of water still declines.
This may happen because the rain falls over short periods or is not adequately absorbed by soil or water storage systems like reservoirs. Consequently, even with rain, the long-term water supply remains disrupted.
2025: Wet Dry Season in Indonesia
Although Indonesia has entered the dry season since April, rainfall continues in several regions. The BMKG, via its official website, has predicted that the 2025 dry season will be wetter than usual, with around 26 per cent of the country experiencing above-normal rainfall.
The regions most affected by wet drought are those with monsoonal rain patterns, such as Java, Bali, and Nusa Tenggara. Typically, these areas experience clearly defined dry and rainy seasons with one distinct peak each.
This year, the rainfall observed during the dry period has disrupted this pattern. It is expected to persist until August 2025, before giving way to a transitional season from September to November, and finally, the rainy season from December 2025 to February 2026.
This anomaly is also linked to warmer-than-average sea surface temperatures around Indonesia, despite the absence of major climate disruptions such as El Niño or the Indian Ocean Dipole (IOD).
These warm temperatures promote the formation of convective clouds, resulting in rain even during the dry season.
Cover: Photo by Pradamas Gifarry on Unsplash
