EI Niño/La Niña Status
Updated on 18 May 2026
The El Niño – Southern Oscillation (ENSO) monitoring system state is “El Niño Watch”. The Nino3.4 index was within the ENSO-neutral range in April 2026, however there are signs in the tropical Pacific that support El Niño conditions developing (e.g., sustained warmer subsurface ocean temperatures). Key atmospheric indicators (cloudiness and trade wind anomalies) supported ENSO-neutral conditions overall in April. The Nino3.4 index was -0.05°C for April 2026 and -0.47°C for the three-month average February – April 2026 based on the Relative Oceanic Nino Index.
ENSO-neutral conditions are predicted to persist in May 2026, with a transition to El Niño conditions predicted in June-July 2026.
Short note on the Indian Ocean Dipole: The Indian Ocean Dipole (IOD) is neutral and predicted to remain neutral until at least June 2026. There is potential for a positive IOD to develop in July-August 2026.
Further Information on ENSO
ENSO conditions are monitored by analysing Pacific sea surface temperatures (SSTs), low level winds, cloudiness (using outgoing longwave radiation), and subsurface temperatures. Special attention is given to SSTs, as they are one of the key indicators used to monitor ENSO. Here, three different datasets are used: HadISST1.1, ERSSTv5, and COBE2 datasets. The Relative Nino3.4 index is used, which compares the SSTs in the Nino3.4 region with the tropical average, accounting for long-term and other shifts in the climate.
El Niño (La Niña) conditions are associated with warmer (colder) SST anomalies in the central and eastern Pacific. The threshold for an El Niño (La Niña) in the Nino3.4 Region is above 0.6°C (below -0.6°C). El Niño (La Niña) conditions also correspond to an increase (decrease) in cloudiness around or to the east of the international dateline (180°), with a decrease (increase) in cloudiness in the west. There is also a decrease (increase) in the trade winds in the eastern Pacific. Sub-surface temperatures in the eastern Pacific should also be warmer (colder) than average, to sustain the El Niño (La Niña) conditions.
International climate centres use different criteria, including different SST thresholds, suitable for their own region and applications. Therefore, variations between centres on the current ENSO state should be expected, especially when conditions are borderline.
The sea surface temperatures (SSTs) in the tropical Pacific in April 2026 were below- to near-average in the central portion of the region and a mix of below- to above-average in the west (Figure 1). The cool (negative) anomalies in the Nino3.4 region (red box) have further reduced compared to the previous month, indicative of neutral conditions during April. Across the Indian Ocean, SSTs were near-average over most of the equatorial region, indicative of a neutral IOD state.
Figure 1: Relative SST anomalies (to the average tropical SST anomaly) for April 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. The index passed the La Niña threshold in September 2025 and returned to the neutral range in March 2026. For La Niña conditions to be present, 1-month 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, predict the index to continue warming, with a transition to El Niño conditions very likely during June-July 2026. The El Niño conditions are predicted to persist at least until October 2026, with most models predicting the strength of the El Niño conditions to be moderate or strong. However, there is still uncertainty in the long-term forecasts at this time of the year, therefore the strength of the predicted El Niño conditions is uncertain.
Figure 3: Forecasts of Relative Nino3.4 strength until October 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
During the Southwest Monsoon months from June to September the correlation of ENSO with rainfall over Singapore is strong, (Figure 5), i.e. if El Niño or La Niña conditions are present, the rainfall patterns are likely to be influenced, particularly by a moderate or strong event (although there can still be considerable variability at the monthly timescale). When there are no El Niño or La Niña conditions present (i.e. ENSO-neutral), there is a large variability in rainfall (Figure 6).
Figure 5: Correlation between total 3-month seasonal rainfall (averaged over Singapore stations) and seasonal Nino3.4 index from 1991-2025. The statistically significant correlations at the 95% level (±0.34) in grey, and at 99% level (±0.43) in red.
Figure 6: Singapore rainfall anomalies for June –October (as a departure from the 1991-2020 long-term rainfall average) arranged in the order from strong La Niña (left) to strong El Niño (right). Orange 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).