[El Niño / La Niña]In October 2026, the sea surface temperature (SST) in the NINO.3 region was above normal with a deviation of +4.4°C. It exceeded the previous record of +4.0°C set in September 2026, the highest since records began in 1949 (Fig.3, Fig.11 and Table). The five-month running mean value of the NINO.3 SST deviation for August 2026 was +3.2°C, remaining above the threshold for the fifth consecutive month (Fig.1 and Table). SSTs in the equatorial Pacific were significantly above normal in the central and eastern parts and below normal in the western part (Fig.4 and Fig.6). Subsurface water temperatures in the equatorial Pacific were significantly above normal in the central and eastern parts, and below normal in the western part (Fig.5 and Fig.7). In the atmosphere, convective activity was enhanced in the vicinity of the equatorial dateline and to its east, and easterly winds in the lower troposphere (i.e., trade winds) over the central equatorial Pacific were significantly weaker than normal (Fig.8, Fig.9 and Fig.10). These oceanic and atmospheric conditions indicate that El Niño features have been steadily strengthening since boreal spring 2026. The El Niño event, which is considered to have persisted in the equatorial Pacific since boreal spring 2026, has reached its strongest intensity on record.
The coupled atmosphere-ocean model predicts that atmosphere-ocean interactions will continue to maintain significant subsurface warm water in the central and eastern parts of the equatorial Pacific until the first half of boreal winter. As a result, the NINO.3 SST deviation is expected to increase, and the El Niño event is expected to continue developing and reach its peak during the first half of boreal winter. From the latter half of boreal winter to spring 2027, the subsurface warm water is expected to gradually weaken. Accordingly, the NINO.3 SST deviation is expected to decrease, but remain above normal (Fig.11). In conclusion, the El Niño event is expected to peak during the first half of boreal winter and is virtually certain (100%) to continue until boreal spring 2027.
[Western Pacific and Indian Ocean]
The area-averaged SST in the tropical western Pacific (NINO.WEST) region was below normal in October (Fig.3). The index is likely to be below normal until boreal spring 2027 (Fig.12).
The area-averaged SST in the tropical Indian Ocean (IOBW) region was above normal in October (Fig.3). The IOBW index is likely to be above normal until boreal spring 2027 (Fig.13). The Indian Ocean Dipole Mode Index (DMI) was +0.69. SSTs in the tropical Indian Ocean were above normal, particularly in the western region (Fig.3 and Fig.4).
[Impacts]
The following weather conditions observed in October were consistent with those in the months of October during the past El Niño events.
- Above normal temperatures from the southern Philippines to Java, from the northern Indochina Peninsula to the Indian Ocean, from northern South America to the tropical central Pacific, in eastern Brazil, and in southeastern Australia.
- Below normal temperatures in southern Polynesia.
- Above normal precipitation in southern Brazil and the surrounding areas.
- Below normal precipitation in South Asia, in northern South America and the surrounding areas, and from southwestern Polynesia to southern Southeast Asia.
The seasonal climate outlook for Japan is available here
Composite analyses for ENSO impacts are available here
