A phenomenon rarer than a solar eclipse and more powerful than any single storm system is unfolding this fall, and NASA is tracking it closely.

El Niño is a natural climate pattern that emerges roughly every two to seven years marked by warmer-than-normal water temperatures in parts of the equatorial Pacific. NASA scientists are keeping watch as it flips trade winds, redistributes ocean heat, scrambles rain patterns, and raises sea surface height across parts of the Pacific.

As of October, the National Oceanic and Atmospheric Administration (NOAA) has said that there’s an 83% chance that the strongest El Niño since 1950 is currently unfolding. People around the world, including farmers, firefighters, and coastal communities, are already experiencing the effects in different ways.

Follow along with these maps as NASA tracks El Niño from its epicenter in the equatorial Pacific Ocean.

One of the first clues appeared in satellite imagery in January 2026, when a swell of warm water called a Kelvin wave was spotted near Micronesia in the western Pacific. Kelvin waves are slow-moving pulses of water thousands of miles long. Like underwater freeways, they transfer heat from west to east across the Pacific. The warm water heats the air directly above it, making it rise. The change in air pressures weakens or even reverses the trade winds that typically blow in the opposing direction, from the Americas toward Asia, causing sea levels in the eastern Pacific to rise further, and waters to warm even more. This chain reaction signifies the start of an El Niño.

The map above shows that by early April, those Kelvin waves had reached the eastern Pacific, and sea surface temperatures had begun to warm. Warm water expands in volume, elevating local sea levels in some areas by as much as 1 to 1.3 feet (30 to 40 centimeters). The higher-than-normal water can be seen sloshing toward South America then moving up the coast to California. Sea levels that are six to eight inches (15 to 20 centimeters) lower than normal are visible around Indonesia and northern Australia.

“Kelvin waves are like the heartbeat of El Niño,” said Josh Willis, project scientist for sea level missions at NASA’s Jet Propulsion Laboratory in Southern California. “And our sea level satellites let us peer into the ocean and watch every beat.”

Scientists have used satellite altimetry to track the height of the ocean with ultraprecision since 1993. That unbroken data record continues today with the Sentinel-6 satellites . State-of-the-art radar altimeters aboard these satellites survey millions of square miles of ocean in a single day, complementing NOAA’s fleet of ocean sensors and buoys drifting and diving through the water below.