Observed Oceanic Drivers for the Previous Season
From August to October 2025, global sea-surface temperatures (SSTs) stayed broadly above average, with the extratropical North Pacific standing out for its pronounced warmth.1 In the equatorial Pacific, SSTs near the Date Line (Niño 4 region) cooled modestly, yet seasonal averages hovered near zero. Elsewhere, Niño indices trended toward slightly cooler. Despite these near-average anomalies in the central and eastern equatorial Pacific, enhanced east-west SST gradients sustained coupled ocean-atmosphere signals characteristic of a weak La Niña, most evident in rainfall anomalies.
The Indian Ocean Dipole (IOD) declined further into its negative phase, primarily driven by sustained above-normal SSTs in the eastern Indian Ocean near Indonesia. In the Atlantic basin, SST anomalies in the North Tropical Atlantic (NTA) were above average, while the South Tropical Atlantic (STA) remained near zero. Above-normal SSTs also persisted across the extratropical North Atlantic.
Outlook for Oceanic Drivers for the Next Season
For December-February (DJF) 2025/26, SST anomalies in the Niño 3.4 and Niño 3 regions are forecast to decline, consistent with a weak La Niña. Persistently above-average SSTs in the western Pacific are expected to sustain a pronounced east-west gradient, reinforcing La Niña-like atmospheric conditions across the equatorial Pacific.
The IOD index is projected to transition from negative values toward near-average conditions. In the equatorial Atlantic, SSTs in the northern tropics are forecast to remain slightly above normal, while the southern tropics are expected to stay near normal.
Surface Temperature Outlook for the Next Season
For DJF 2025/26, the multi-model ensemble forecast indicates a strong global signal for enhanced probabilities of above-normal land surface temperatures, with high model agreement across much of the Northern Hemisphere above 30oN. Southern and northeastern regions of North America, Central America, the Caribbean, and the Arctic Circle all show elevated probability for above-normal conditions, supported by robust model consistency. Small regions lacking a consistent signal include the northwestern part of North America, the interior of the Indian subcontinent, and Southeast Asia.
In the Southern Hemisphere, enhanced probabilities for above-normal temperatures are predicted over New Zealand and southern regions of South America, while most of Australia shows weak enhancement in probabilities for above-normal temperature.
In the tropics, strong enhancement in the probability of above-normal temperatures is forecast across equatorial Africa and the Maritime Continent. These regions also exhibit moderate to strong model agreement, reinforcing the likelihood of above-normal conditions.
Over the oceans, widespread above-normal temperatures are projected across the North Pacific, the western Atlantic north of the equator, and the eastern Indian Ocean, with strong model agreement supporting the signal. Elsewhere in the extratropical oceans, the extent of below-normal conditions is limited to southern oceans along 60°S. Over the equatorial Pacific east of the Date Line, probabilities for below-normal temperatures are enhanced, while the region from 120°W to the coastal waters of South America shows increased probabilities for near-normal conditions.
Rainfall Outlook for the Next Season
For DJF 2025/26, rainfall predictions in the equatorial Pacific are consistent with weak La Niña conditions, amplified by an enhanced positive east-west sea-surface temperature gradient. Enhanced probabilities for below-normal rainfall extend eastward from 170°E to near 170°W, where the signal bifurcates into northern and southern branches. The northern branch continues eastward toward the western coast of South America, while the southern branch arcs southeastward to near 120°W. Along the equator, probabilities for near-normal rainfall are forecast from 170°W to the western coast of South America.
Overall, the DJF 2025/26 rainfall outlook reflects a La Niña-influenced pattern, with suppressed rainfall across the central and eastern Pacific and enhanced rainfall over the western Pacific and adjacent land regions. Beyond the Pacific, enhanced probabilities for below-normal rainfall are predicted over the southern equatorial Atlantic, southern North America, eastern Asia, northeastern South America, and the western Indian Ocean. In contrast, probabilities for above-normal rainfall are increased across the eastern Maritime Continent, the Philippine Sea, northern North America, southern Central America, the Caribbean, northern Europe, and northern Asia north of 50°N.
1 https://www.cpc.ncep.noaa.gov/products/people/mchen/AttributionAnalysis…
