Enviro News Asia, Jakarta — The Meteorology, Climatology, and Geophysics Agency (BMKG) has issued a nationwide alert urging all sectors to prepare for the peak of the rainy season, which is forecast to occur between November 2025 and February 2026.
As of the end of October, 43.8 percent of Indonesia’s regions, equivalent to 306 Seasonal Zones (ZOM), have officially entered the rainy season. This transition marks the beginning of increased risks of extreme weather, including heavy rainfall, strong winds, and tropical cyclone activity over southern Indonesia.
BMKG Head Dwikorita Karnawati stated that rainfall has begun spreading from the western to eastern regions of the archipelago and will intensify over the coming weeks.
“We are entering the transition period toward the peak of the rainy season. Communities must stay alert for extreme weather events such as heavy rain accompanied by strong winds and lightning, particularly across southern Indonesia influenced by tropical cyclone systems from the Indian Ocean,” she said during a press conference in Jakarta on Saturday (November 1, 2025).
High Rainfall and Increasing Weather Hazards
BMKG’s analysis indicates that high to very high rainfall, exceeding 150 millimeters per ten days, is expected in several regions, including Banten, West Java, Central Java, East Java, Bali, Nusa Tenggara, West Kalimantan, Central Kalimantan, East Kalimantan, South Sulawesi, and Central Papua.
In the past week, extreme rainfall was recorded in Tampa Padang, West Sulawesi (152 mm/day); Torea, West Papua (135.7 mm); and Naha, North Sulawesi (105.8 mm). Between October 26 and November 1, 2025, BMKG documented 45 extreme weather incidents, mostly caused by heavy rain and strong winds leading to floods, landslides, and structural damage.
Despite rising rainfall, daily maximum temperatures remain high, reaching 37°C in Riau and above 36°C in parts of Sumatra and Nusa Tenggara, indicating unstable atmospheric conditions that could trigger sudden extreme weather.
Atmospheric Dynamics and Tropical Cyclone Risk
Dwikorita explained that several atmospheric factors are currently active, including the Madden-Julian Oscillation (MJO), Rossby and Kelvin waves, and positive sea surface temperature anomalies around Indonesian waters, all contributing to increased cloud formation.
“The combination of these factors intensifies the likelihood of heavy rainfall and storms across many regions. Therefore, communities must continue monitoring BMKG’s early warnings,” she emphasized.
BMKG also warned of heightened tropical cyclone potential in the southern Indian Ocean, which could bring extreme rainfall and strong winds to coastal areas of Java and Nusa Tenggara. The tropical cyclone period in southern Indonesia typically begins in November, and low-pressure systems forming near the Indian Ocean may evolve into tropical cyclones capable of triggering flooding and coastal storms.
“Cyclones developing over the Indian Ocean can cause drastic rainfall increases and major floods in coastal regions. Local governments must ensure infrastructure readiness and community preparedness for potential disasters,” Dwikorita added.
La Niña Development and Rainfall Outlook
BMKG’s sea surface temperature monitoring in the Pacific Ocean shows a weak La Niña phase emerging, with temperature anomalies reaching -0.54°C in September and -0.61°C in October. Despite this development, BMKG predicts normal rainfall conditions across Indonesia from November 2025 to February 2026, suggesting that La Niña’s impact will remain minimal.
Weather Modification and Mitigation Efforts
As part of mitigation measures, BMKG, in coordination with BNPB and related agencies, has conducted Weather Modification Operations (OMC) in Central Java and West Java to reduce flood and landslide risks. The operations have successfully decreased rainfall intensity by 43.26% in Central Java and 31.54% in West Java.
“OMC is a real example of how science and inter-agency collaboration can directly support communities in facing hydrometeorological disasters,” said Dwikorita.
Public Advisory and Safety Measures
BMKG urges the public to remain vigilant and cautious during sudden weather changes. People are advised to avoid open spaces, tall trees, and weak structures during heavy rain accompanied by lightning and strong winds.
Additionally, the ongoing heat in several regions calls for proper hydration and sun protection. Communities living in flood-prone and hilly areas are also encouraged to strengthen preparedness against floods, flash floods, and landslides.
“If managed properly, this longer-than-usual rainy season can benefit agriculture and strengthen national food security,” Dwikorita concluded. (*)
