BMKG forecasts low September–October rainfall and drought risk in NTT

Labuan Bajo — Indonesia’s meteorological agency BMKG is forecasting predominantly low rainfall across East Nusa Tenggara (NTT) during the second and third ten‑day periods of September 2026 and the first ten days of October, as part of a wider pattern of dry conditions linked to a very strong El Niño.

The forecast covers three ten‑day windows: 11–20 September, 21–30 September and 1–10 October 2026, and classifies much of Indonesia’s rainfall during these periods in the low‑to‑medium range of 0–150 millimetres per ten days, with many areas expected to receive less than 50 millimetres per ten days according to BMKG’s climate outlook.

In its analysis of atmospheric dynamics for the first ten days of September, issued on 9 September 2026, BMKG reports that 92.62% of the assessed Indonesian area recorded low rainfall in that initial period, and 92.86% experienced rainfall below normal levels. The same bulletin notes that 80.7% of Indonesia’s 564 climate‑zone areas were in the dry season, with NTT among the provinces with zones classified as experiencing dry conditions.

Rainfall thresholds and affected regions

BMKG uses a ten‑day classification in which rainfall below 50 millimetres per period is considered low. Its seasonal projections and weekly weather outlook describe rainfall during the September dasarian sequence as generally remaining in the low‑to‑medium band across much of the country, including NTT.

Low‑rainfall areas for September and October are forecast to include parts of Sumatra, Java, Bali, West Nusa Tenggara, NTT, Kalimantan, Sulawesi, Maluku and portions of Papua, with the exact distribution shifting between ten‑day windows. BMKG’s monthly climate guidance also indicates that NTT has a high probability of monthly rainfall below 50 millimetres in October, with parts of the province expected to remain in that category into November.

BMKG’s national climate pages explain that these outlooks are based on monitoring large‑scale climate drivers, including the Indian Ocean Dipole (IOD) and the El Niño–Southern Oscillation (ENSO). For the first ten days of September 2026, the agency reports a Nino3.4 sea‑surface temperature anomaly of about +2.76 degrees Celsius, a value BMKG associates with a very strong El Niño phase.

Meteorological drought warnings in NTT

In addition to rainfall forecasts, BMKG has issued early warnings for meteorological drought in NTT. The national drought early‑warning table lists multiple NTT districts under the Alert (Waspada), Standby (Siaga) and Warning (Awas) categories for September, reflecting extended periods without rain and a high probability of continued dry conditions.

Local and national media reporting on BMKG’s early‑warning bulletin state that more than 200 sub‑districts (kecamatan) across NTT are under meteorological drought status for the first ten days of September 2026, spread across 22 regencies and cities. According to this coverage, BMKG’s classification is based on the number of consecutive days without rain and the probability of low rainfall, with Alert indicating more than 21 dry days, Standby more than 31 days and Warning more than 61 days combined with a high likelihood of continued dryness.

BMKG and regional climate‑early‑warning services emphasise that, despite the broad dry‑season pattern, there is still some chance of light rainfall at certain locations in NTT during early September, including coastal and island areas, even as interior districts face prolonged dry spells.

Forecasts versus observed conditions

BMKG distinguishes clearly between forecast data and observed rainfall. Its analysis for the first ten days of September 2026 provides national‑scale statistics on how much rain fell and whether it was above or below normal, but these figures describe Indonesia as a whole and are not a direct measurement for each district in NTT.

The ten‑day rainfall forecasts for 11–20 September, 21–30 September and 1–10 October 2026 are projections based on numerical models and climate indicators. They signal a need for water managers, farmers and local authorities in NTT to plan for limited rainfall through early October, but decisions about specific districts, crops or village‑level water supplies will require more detailed local data than is available in the national‑scale bulletin.

Sources

• Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) – Analisis Dinamika Atmosfer Dasarian I September 2026
• Media Indonesia – "Kekeringan di NTT: 212 Kecamatan Terancam, 66 Berstatus Awas Akibat El Nino Kuat"
• CNBC Indonesia – "BMKG Ungkap Wilayah RI Terancam Kekeringan Efek El Nino, Ini Daftarnya"
• Metro TV News – "BMKG Keluarkan Peringatan Dini Kekeringan hingga 20 September 2026, Cek Wilayahnya"