Review of Regional Weather for March 2026

1. Overview

1.1 During March 2026, below-average rainfall was recorded over much of the Maritime Continent with a mix of below and near-average rainfall over most of Mainland Southeast Asia (Figure 1). Mix of below- to above-average (wetter) anomalies were also observed over parts of the eastern equatorial region for both datasets (GSMaP-NRT and CMORPH-CRT). There were dry anomalies over much of central and southern Mainland Southeast Asia, with some regions of above-average rainfall over parts of Viet Nam and northern Myanmar. The largest positive (wetter) anomalies were recorded over Papua for GSMaP-NRT, and over northern Myanmar and western Sumatra for CMORPH-CRT, with the largest negative (drier) anomalies over northwestern Borneo for both datasets.

1.2 The observed rainfall anomaly pattern of below-average rainfall over the Maritime Continent, where the highest anomalies are recorded, is consistent with the predictions from the subseasonal weather outlooks for March 2026 (2 – 15 March 2026 and 16 – 29 January 2025). The subseasonal weather outlooks predicted a drier central Maritime Continent, which is more consistent with the recorded rainfall from CMORPH-BLD. The below-average rainfall over the Maritime Continent is also consistent with the seasonal rainfall outlook for March, with higher confidence of below-normal rainfall over the central region predicted.

Figure 1: Rainfall anomalies for March 2026 based on GSMaP-NRT data (left) and CPC CMORPH-CRT data (right). The climatological reference period is 2001-2024. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 Above-average temperature was recorded over parts of northeastern Mainland Southeast Asia, with below- to near-average temperature for southeastern and northwestern Mainland Southeast Asia (Figure 2). Below-average temperature was recorded for the northeastern and southeastern Maritime Continent, while near- to above-average temperature was recorded for western and central Maritime Continent. The warmest anomalies (2°C – 3°C above average) were recorded over northern Viet Nam, while the coolest anomalies (0.5°C – 1°C below average) were recorded over eastern Myanmar, northern Philippines and eastern Cambodia.

Figure 2: Temperature anomalies for March 2026 based on ERA-5 reanalysis. The climatological reference period is 2001-2024. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) was inactive for much of March based on the RMM diagram (Figure 3). The signal was inactive during the beginning of March, then emerged shortly in Week 3 over the Western Pacific (Phase 7), propagating to Western Hemisphere (Phase 8) and then decayed over the Western Hemisphere (Phase 8) in the same week. The MJO signal remained indiscernible for much of Week 4, before emerging over the Western Hemisphere (Phase 1) at the end of the month. At this time of the year, Phases 7 and 8 tend to bring drier conditions to the Maritime Continent, with the observed rainfall in March also showing drier conditions.

Figure 3: The MJO phase diagram. The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator (denoted in the text with the first day of the month in blue and the last day of the month in red). The distance of the index from the centre of the diagram is related to the strength of the MJO. Values within the grey circle are considered weak or indiscernible (data from the Bureau of Meteorology, Australia).

2.2 The El Niño – Southern Oscillation (ENSO) condition is “Neutral”. The Indian Ocean Dipole (IOD) is currently in the neutral state.

Subseasonal Weather Outlook and Review