How the monsoon unfolds this season may depend on the balance between Pacific warming and weather patterns developing in the Indian Ocean | Photo Credit: ROY CHOWDHURY A

Sea surface temperatures (SSTs) crossed the drought-bearing El Nino threshold of +0.80°C as of June 7, while the Indian Ocean Dipole (IOD) could turn positive during August-September, boosting the prospects of the South-West monsoon, Australia’s Bureau of Meteorology (BoM) has said.

The recent relative Nino 3.4 index value, which measures the sea surface temperature (SST) anomalies in the central-to-eastern equatorial Pacific, for the week ending June 7, 2026, is +0.81°C; this is just above the El Nino threshold (+0.80°C), BoM said in its Southern Hemisphere Monitoring report. All models, including the Bureau’s, indicate the tropical Pacific will continue to warm over the coming months.

On the other hand, the IOD is currently neutral. As of June 7, 2026, the IOD index was -0.34°C. Forecasts are still uncertain, but most models suggest neutral conditions will continue at least through June and August, with the possibility of a positive IOD event developing in August-September, said the Australian weather agency.

IOD positive impact

​A positive IOD can bring more moisture to India, often helping monsoon rains even in an El Nino year. IOD is a climate phenomenon caused by variations in sea temperatures in the Indian Ocean. Its positive, negative and neutral phases can influence the Indian monsoon.

The development comes on the heels of the India Meteorological Department (IMD) lowering its forecast for the South-West Monsoon to receive 90 per cent of the long-period average rainfall. The monsoon, which set in 3 days late this year on June 4, is currently 18 per cent deficient.

Months of warming have brought the tropical Pacific one step closer to El Nino conditions. Weakening trade winds and the falling pressure patterns suggest the atmosphere is beginning to catch up, said BoM.

Uncertainty over strength

​If these trends persist, an El Nino event is likely in the coming months, with forecasts indicating further warming over the tropical Pacific. All models, including the Bureau’s, indicate the tropical Pacific will continue to warm over the coming months.

​The report said there was still some uncertainty about the strength of this El Nino. Global models suggest that it will be at least moderate strength with the possibility of a strong event depending on how much warming occurs in the central tropical Pacific.

​A strong El Nino signal in the Nino3.4 region does not necessarily translate into a strong impact, as ENSO is only one of many factors that can influence seasonal weather and climate.

​Atmospheric Shift

​As of June 7, 2026, the 30-day Southern Oscillation Index (SOI) is -21.7. The SOI index values at days 60 and 90 are −14.9 and −9.5, respectively.

​The Southern Oscillation Index (SOI) is a measure of the strength of ENSO (El Nino–Southern Oscillation) based on the differences in air pressure between Tahiti and Darwin, Australia.

​Trade winds are weaker than normal across the tropical Pacific, but there has been no persistent change in the pattern of cloudiness near the date line. 

​Collectively, these indicators suggest that the atmosphere is starting to respond to the SST signal in the tropical Pacific and is showing early stages of the ocean–atmosphere coupling needed for an established event.

​The SST analysis for the week ending June 7, 2026 shows average to above-average waters around most of Australia. Waters are particularly warm along the coasts of New South Wales and eastern Tasmania (up to around 3 to 4°C above average). “This SST pattern will likely continue for the next several months,” the report added.

Published on June 9, 2026