El Ni\u00f1o, characterized by warmer-than-normal water temperatures in parts of the equatorial Pacific, made its return in June 2026. Observations of sea surface height from the\u00a0Sentinel-6 Michael Freilich<\/a>\u00a0satellite that month indicated that the 2026 event was continuing to strengthen. \u00a0<\/p>\n The natural, recurring phenomenon can have widespread effects, typically bringing wetter conditions to the U.S. Southwest and drought to countries in the western Pacific, such as Indonesia and Australia. NOAA declared an El Ni\u00f1o<\/a> on June 11, after sea surface temperatures in the central and eastern equatorial Pacific measured at least 0.5 degrees Celsius above average for several consecutive months.<\/p>\n Meanwhile, NASA scientists have been observing a complementary sign of El Ni\u00f1o: areas of elevated sea surface height. When ocean water warms, it expands in volume and causes the sea surface to rise\u2014making the water\u2019s height a reliable indicator of ocean temperatures. Warmer-than-normal temperatures, hence higher sea surface heights, in parts of the equatorial Pacific Ocean are associated with El Ni\u00f1o.<\/p>\n The map above depicts\u00a0sea surface height<\/a>\u00a0anomalies across the central and eastern Pacific Ocean as observed on June 8, 2026. Shades of red indicate sea levels that were higher than average. Normal sea level conditions appear white, and lower areas are blue. \u00a0<\/p>\n Data for the map were acquired by the\u00a0Sentinel-6 Michael Freilich<\/a> satellite\u2014launched in 2020 by NASA and led by ESA (European Space Agency)\u2014and processed by scientists at NASA\u2019s Jet Propulsion Laboratory (JPL). Note that signals related to seasonal cycles and long-term trends have been removed to highlight sea level anomalies associated with El Ni\u00f1o and other short-term natural phenomena.<\/p>\n Earlier in spring 2026, the satellite started to detect precursor signs of El Ni\u00f1o<\/a> as swells of warm water hundreds of miles wide, known as Kelvin waves, moved from the western Pacific to the eastern Pacific. That happens when trade winds in the western equatorial Pacific weaken and then temporarily reverse to blow from the west. Warm water piles up in the east, deepening the warm surface layer, lowering the\u00a0thermocline<\/a>, and suppressing the upwelling that usually keeps waters along the Pacific coasts of the Americas cooler.<\/p>\n This buildup of heat beneath the water\u2019s surface is what sea surface height observations capture. It goes beyond surface temperature measurements to indicate how much heat is stored in the subsurface. That\u2019s important because a shallow warm layer might not have much impact on climate and weather, while a large reservoir of heat below the surface can matter more.<\/p>\n According to JPL sea level researcher Severine Fournier, deputy project scientist for Sentinel-6 Michael Freilich, conditions in the western Pacific on June 8 looked similar to those from the same time in 1997, a year when an exceptionally strong El Ni\u00f1o emerged. Warm conditions in the eastern Pacific in 2026 have lagged behind, however, with fewer Kelvin waves built up by the same date.<\/p>\n Still, more warm Kelvin waves appeared to be approaching the eastern Pacific, meaning El Ni\u00f1o was still strengthening. Whether it catches up to 1997 depends on ocean activity in the coming weeks. \u201cFor now, it looks like it\u2019s going to be a big one\u2014more so than I would have said last week\u2014but we still need more observations to know what\u2019s going to happen.\u201d<\/p>\n NASA Earth Observatory image by Lauren Dauphin, using modified Copernicus Sentinel data (2023) processed by the European Space Agency and further processed by Josh Willis, Severin Fournier, and Kevin Marlis\/NASA\/JPL-Caltech. Story by Kathryn Hansen.<\/em><\/p>\n![\"A](\"https:\/\/assets.science.nasa.gov\/dynamicimage\/assets\/science\/esd\/eo\/images\/iotd\/2026\/el-ni\u00f1o-is-underway\/elnino_sen6_20260608_lrg.jpg?w=2909&h=1939&fit=clip&crop=faces%2Cfocalpoint\")
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