El Niño Causes Rainy Season to Delay Until December
The Meteorology, Climatology, and Geophysical Agency (BMKG) predicts that the start of the rainy season will occur between December 2026 and February 2027. BMKG stated that the beginning of the rainy season in Indonesia is delayed or arriving later, caused by the El Niño phenomenon.
“The combination of the El Niño and IOD (Indian Ocean Dipole) phenomena occurring simultaneously is exacerbating and prolonging the drought period in most parts of Indonesia, resulting in a delayed and shorter rainy season,” said the Head of BMKG, Faisal Teuku Faisal Fathani, during a press conference on the ‘Rainy Season Prediction’ at the BMKG MHEWS building, Jakarta, on Tuesday (22/9/2026).
BMKG predicts that for the 2026-2027 rainy season period, 529 Seasonal Zones (ZOM), or 61.08% of Indonesia’s territory, will experience a delay from the climatological average. The very strong intensity of El Niño and the Indian Ocean Dipole in the oceans surrounding Indonesia are impacting rainfall levels by reducing precipitation.
“The start of the rainy season in most parts of Indonesia is predicted to arrive later or be delayed, affecting 529 seasonal zones (ZOM) or 61.08% of Indonesia’s land area,” explained Faisal.
Short Rainy Season 202long/2027, but with Higher Rainfall
The Acting Deputy of Meteorology at BMKG, Andri Ramdhani, noted that the duration of this rainy season is relatively shorter. However, the accumulation of rainfall is predicted to be above normal, meaning there is a high potential for heavy rainfall with high intensity.
“This rainy season period is short, but rainfall is generally higher than normal. This is what needs to be watched,” said Andri during the press conference regarding the 2026/2027 rainy season prediction in Indonesia, held at the BMKG Central office, Jakarta, on Tuesday (22/9/2026).
“Therefore, heavy rain could occur intensely during those months, and regions that have historically experienced wet hydrometeorological disasters need to be on alert,” he added.
Peak of the Rainy Season to Last Three Months
At the same opportunity, the Director of Climate Change at BMKG, Fachri Radjab, explained that the peak of the rainy season is expected to be concentrated within a three-month period, namely December 2026, January 2027, and February 2027.
In December 2026, approximately 155 Seasonal Zones (ZOM), or 36.94% of Indonesia’s land area, are predicted to enter the peak of the rains. This includes most of Sumatra, northern Kalimantan, West Kalimantan, and parts of western Sulawesi.
By January 2027, the peak of the rainy season will shift to cover 162 ZOM, or 25.68% of the land. This area includes almost the entire island of Java, Lampung, South Kalimantan, most of Sulawesi (northern Sulawesi and western South Sulawesi), and the majority of Papua.
Meanwhile, in February 2027, the peak of the rainy season will occur in 190 ZOM, covering most of central Sulawesi, Southeast Sulawesi, southern Papua, and several points in Maluku.
“What we also need to be wary of is that this peak of the rainy season is quite concentrated. This means it occurs most intensely within these three months: December, January, and February. This is what requires our vigilance,” concluded Fachri.
BMKG: 25 Provinces Have Experienced No Rain for Over 60 Days
Furthermore, BMKG stated that the impact of the 2026 El Niño is expanding and worsening the drought in Indonesia. It is recorded that 25 provinces across the country have now experienced consecutive rainless days (HTH) for more than 60 days.
The Deputy of Climatology at BMKG, Ardhasena Sopaheluwakan, mentioned that the area experiencing the most extreme rainless days and drought is currently Bantul, Special Region of Yogyakarta (DIY).
“Many observation locations have reported consecutive rainless days of more than 60 days, spread across 25 provinces, with the longest rainless period currently in the Bantul area, lasting 131 days or more than 4 months,” said Ardhasena on Tuesday (22/9/2026).
Historically, he continued, El Niño always extends and worsens the dry season in Indonesia, particularly in regions south of the Equator. This phenomenon is predicted to persist until early next year.
“The current phenomenon will persist at least until the end of the first quarter of 2027. However, its impact on drought in Indonesia will conclude with our entry into the rainy season,” he explained.
Ardhasena added that the impact of this year’s climate anomaly has even created anomalies in Indonesia’s climate zones. Regions that are naturally accustomed to rainfall throughout the year are now also being affected by the dry season.