EI Niño/La Niña Status

Updated on 20 March 2026

The El Niño Southern Oscillation (ENSO) monitoring system state is “La Niña Conditions”. The Nino3.4 index shows La Niña conditions are weakening but still indicates La Niña in February 2026. Key atmospheric indicators (cloudiness and trade winds in the central Pacific) also support the presence of La Niña conditions in February, although subsurface ocean temperatures support a transition away from La Niña conditions soon. The Nino3.4 index was -0.8°C for February 2026 and 1.0°C for the December 2025 – February 2026 based on the Relative Oceanic Nino Index.

La Niña conditions are predicted to continue weakening and transition to ENSO-neutral conditions in March – April 2026. Models predict the ENSO-neutral conditions to persist at least until May 2026, with either ENSO-neutral continuing or El Niño conditions developing in June-July 2026.

Short note on the Indian Ocean Dipole: While the Indian Ocean Dipole (IOD) index had a positive value in February 2026, a positive IOD state is not expected to become established, with models predicting the IOD to be neutral in March – April 2026.

Further Information on ENSO

The sea surface temperatures (SSTs) over the tropical Pacific in February 2026 were below average in the central and eastern portions of the region and above average in the west, indicative of La Niña conditions (Figure 1) The coolest (negative) anomalies were in the eastern tropical Pacific including the Nino3.4 region (red box). Across the Indian Ocean, the equatorial region was below average in the eastern parts of the region (including the dashed black box). The equatorial region in western part (including the sold black box) was below to near average. While this temperature difference in the Indian Ocean shows a weak dipole pattern in February 2026, a positive IOD is not expected to become established.

Figure 1: Relative SST anomalies (to the average tropical SST anomaly) for February 2026 using ERSST v5 data. Red (blue) shades show regions of relative warming (cooling). The tropical Pacific Ocean Nino3.4 Region is outlined in red. The Indian Ocean Dipole index is the difference between average SST anomalies over the western Indian Ocean (black solid box) and the eastern Indian Ocean (black dotted box).

Looking at the Relative Nino3.4 index in Figure 2, the 1-month Relative Nino3.4 index was negative, but within the neutral range, between March 2025 and August 2025. Since September 2025, index passed the La Niña threshold, although in February 2026 the index weakened, approaching the La Niña threshold. For La Niña conditions to be present, 1-month of cold SST anomalies (observed or forecast) should persist for at least four months below the threshold, with at least one of the months observed; along with supporting atmospheric observations.

Figure 2: The Relative Nino3.4 index using the 1-month SST anomalies. Warm anomalies (≥ +0.6; brown4) correspond to El Niño conditions while cold anomalies (≤ -0.6; blue) correspond to La Niña conditions; otherwise neutral (> -0.6 and < +0.6; grey).

Model outlooks from Copernicus C3S (Figure 3), based on the Relative Nino3.4 SST index, show that models predict the La Niña conditions continue weakening, with a return to ENSO-neutral conditions very likely from March 2026 onwards. From June – July 2026, models predict either ENSO neutral or El Niño conditions, with a higher chance of El Niño conditions. However, there is considerable uncertainty in the long-term forecasts at this time of the year.

Figure 3: Forecasts of Relative Nino3.4 strength until August 2026 from various seasonal prediction models from international climate centres (grey lines). The solid blue and yellow lines note the La Niña and El Niño thresholds used by MSS.

Historical ENSO Variability
To classify a historical El Niño event, the Relative Oceanic Nino Index (RONI, or 3-month average Relative Nino3.4 value), must be above 0.6°C for 5 or more consecutive months. For La Niña events, the threshold is -0.6°C. Otherwise it is considered neutral. ENSO events with a peak value above 1.5°C (El Niño) or below -1.5°C (La Niña) are considered strong. Otherwise, the events are considered weak to moderate in strength. The following figure (Figure 4) shows the development the Relative Nino3.4 index for recent El Niño and La Niña events in comparison to other El Niño/La Niña events.

Figure 4: Relative Oceanic Nino Index (RONI) development and retreat of different El Niño (left)/La Niña (right) events since the 1960s. Recent El Niño and La Niña events are in red and purple, respectively.

Impact of El Niño/La Niña on Singapore

Towards the end of the Northeast Monsoon season and into the first inter-monsoon period, ENSO has a small influence on Singapore’s rainfall (Figure 5). Between February and May, La Niña events tend to bring wetter conditions than El Niño events, although there is still a lot of year-to-year variability (Figure 6).

Figure 5: Correlation between total seasonal rainfall (averaged over Singapore stations) and seasonal Nino3.4 index from 1991-2025 centred on the month indicated (e.g., for June’s value it corresponds to season May-June-July). The statistically significant correlations at the 95% level (±0.34) are underlined, at 99% level (±0.43) in red.

Figure 6: Singapore rainfall anomalies for February – May (as a percentage of departure from the 1991-2020 long-term rainfall average) arranged in the order from strong La Niña (left) to strong El Niño (right). Brown bars denote El Niño years’ anomalies, blue bars denote La Niña years’ anomalies, and grey bars denote ENSO neutral years’ anomalies.

References

Turkington, T., Timbal, B., & Rahmat, R. (2018). The impact of global warming on sea surface temperature based El Nino Southern Oscillation monitoring indices. International Journal of Climatology, 39(2).