- Indonesia’s BMKG forecasts another week of unstable weather driven by a weak La Niña and Asian monsoon, bringing heavy to extreme rain across Java, Bali, and eastern regions through early February 2026.
- After days of torrential rainfall, Indonesia braces for more extreme weather as BMKG cites La Niña and monsoon activity as key factors behind widespread rain and potential flash floods.
- BMKG warns Jabodetabek and several provinces to prepare for intense rainfall, strong winds, and possible disasters linked to atmospheric instability and an active monsoon system.
The Meteorology, Climatology, and Geophysics Agency (BMKG) has warned of continued volatile weather across Indonesia this week, following days of torrential rain and extreme weather that drenched Jakarta, Banten, West Java, and South Sumatra from January 23 to 26, 2026.
In an official statement on its Instagram account, BMKG urged the public to remain alert and take necessary precautions to minimize disaster risks caused by extreme weather, including flooding, flash floods, and landslides.
National Weather Factors for the Week Ahead
According to the Meteorology Deputy of BMKG’s Public Meteorology Directorate, weather conditions in the coming week are influenced by the strengthening negative phase of the El Niño–Southern Oscillation (ENSO). This global climate system, which arises from temperature shifts in the Pacific Ocean, continues to affect rainfall, temperature, and global weather patterns.
Currently, sea surface temperatures in the central and eastern Pacific are cooler than average, signaling a weak La Niña phenomenon. This condition increases the likelihood of more moisture supply, which can form rain clouds over parts of eastern Indonesia.
The Asian monsoon activity is also expected to persist until early February 2026. This monsoon was one of the triggers behind the recent extreme rainfall experienced in the capital region late last week.
Additionally, the Cross Equatorial Northerly Surge (CENS)—a flow of winds from the South China Sea across the equator—along with regions of low pressure over the southern Indian Ocean near Banten, the Gulf of Carpentaria, and northwestern Australia, are forecast to contribute to slow winds over southern Indonesia, allowing rain clouds to develop more easily.
Weather Forecast: January 27–29, 2026
| Alert Level | Regions Affected |
|---|---|
| Alert: Very Heavy to Extreme Rainfall | West Java |
| Standby: Heavy to Very Heavy Rainfall | Bengkulu, Banten, Jakarta, West Java, Central Java, Yogyakarta, East Java, Bali, West Nusa Tenggara (NTB), East Nusa Tenggara (NTT) |
| Moderate Rainfall | West Sumatra, Jambi, South Sumatra, Bangka Belitung Islands, Bengkulu, Lampung, Banten, Central Java, Yogyakarta, East Java, Bali, NTB, NTT, Central/East/North/South Kalimantan, North/Central/West/South Sulawesi, North Maluku, Maluku, Southwest Papua, West Papua, Central Papua, Papua Highlands |
| Strong Winds | Bali, NTT, NTB, West Kalimantan |
Weather Forecast: January 29 – February 1, 2026
| Alert Level | Regions Affected |
|---|---|
| Standby: Heavy to Very Heavy Rainfall | West Sumatra, East Java, NTT, West Kalimantan, South Sulawesi, Papua Highlands |
| Advisory: Moderate Rainfall | West Sumatra, Jambi, South Sumatra, Bangka Belitung, Bengkulu, Lampung, Banten, Jakarta, West Java, Central Java, Yogyakarta, East Java, Bali, NTB, NTT, all regions of Kalimantan and Sulawesi, North Maluku, Southwest Papua, Central Papua, Papua Highlands, Papua |
| Strong Winds | NTB, NTT, South Sulawesi, Maluku, Southwest Papua |
Jabodetabek Forecast: January 27 – February 2, 2026
| Date | Heavy Rain | Moderate Rain | Light Rain |
|---|---|---|---|
| Jan 27–28 | Central, West, East, and North Jakarta; Bekasi Regency; Bogor Regency; Tangerang City; Tangerang Regency | South Jakarta; Thousand Islands; Bekasi City; Depok; South Tangerang; Bogor City | — |
| Jan 28–29 | South and East Jakarta; Bekasi City; Depok; Tangerang City; South Tangerang | Central, West, North Jakarta; Thousand Islands; Bekasi Regency; Bogor Regency; Bogor City; Tangerang Regency | — |
| Jan 29–30 | Tangerang Regency | Jakarta; Bekasi City; Bekasi Regency; Depok; Bogor Regency; Bogor City; Tangerang City; South Tangerang | — |
| Jan 30–31 | — | South and East Jakarta; Bekasi Regency; Bekasi City; Bogor Regency; Depok; South Tangerang | Central, West, and North Jakarta; Thousand Islands; Bogor City; Tangerang City; Tangerang Regency |
| Jan 31 – Feb 1 | — | West and South Jakarta; Thousand Islands; Tangerang City; Tangerang Regency; South Tangerang; Bogor Regency; Bekasi Regency; Depok | Central, East, and North Jakarta; Bekasi City; Bogor City |
| Feb 1–2 | — | West and North Jakarta; Thousand Islands; Bogor Regency; Tangerang City; Tangerang Regency | Central, South, and East Jakarta; Bekasi Regency; Bekasi City; Depok; Bogor City; South Tangerang |
BMKG data show that extreme rainfall in the past week was largely influenced by Asian monsoon activity. Strong wind speeds over the South China Sea brought moist air masses from Asia toward Indonesia.
This led to large cloud formations along the Intertropical Convergence Zone (ITCZ), stretching from the Indian Ocean west of Bengkulu, southern Sumatra, Java, Bali, NTB, NTT, and toward the Arafura Sea.
Additionally, the weakening of Tropical Cyclone Luana into a low-pressure system contributed to the extensive cloud buildup. High humidity and strong atmospheric instability—where air masses freely rise to form tall rain clouds—accelerated the development of heavy rainfall over Indonesia’s southern region, triggering multiple hydrometeorological disasters last week.
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