El Niño Is Waking Up: What It Means for California Monsoons and Hurricane Seasons

A developing El Niño in the Pacific Ocean is beginning to show its first atmospheric effects, with scientists detecting shifts in pressure, wind patterns, and ocean temperatures that could shape weather across the United States in the coming months. Experts have warned for months about the potential for a strong or even "super El Niño" as climate models continue to indicate a pattern that could rival some of the most intense events on record.

The latest observations include warmer-than-normal sea surface temperatures and bursts of westerly winds that help push stored heat from the western Pacific toward the central and eastern Pacific. Severe Weather Europe described the transition as a turning point for summer and potentially the remainder of 2026.

"The 2026 North American summer season is entering a critical transition phase," Severe Weather Europe wrote. "Latest data confirms that a strong El Niño event is not only developing but is already showing early signs of its presence in the global atmospheric circulation.

We are now witnessing the first detectable changes in pressure and temperature patterns across the United States and Canada." If current trends continue, forecasters say the emerging El Niño pattern could influence the jet stream and shift seasonal weather across North America heading into late summer and fall. Those changes could affect rainfall, temperatures, and storm tracks in different ways by region.

For California, El Niño has little direct influence on summer weather. Unlike winter, when shifts in the jet stream can steer storm systems into the state, summer patterns are driven mainly by regional heat, the Pacific high-pressure system, and short-term atmospheric disturbances.

The main indirect connection comes through the eastern Pacific hurricane season. A more active basin during El Niño can increase the chances that tropical systems or their remnants send moisture northward.

In some cases, that moisture can feed into the North American monsoon circulation or contribute to late-season rainfall events across the Desert Southwest, and only rarely into Southern California. Otherwise, monsoon thunderstorms, summer heat, and day-to-day weather patterns in California operate largely independently of El Niño conditions.

El Niño can influence the North American monsoon season, which begins officially on June 15, but the connection is weaker and less consistent than its impact on winter weather. The monsoon is driven mainly by intense summer heating over the Southwest, moisture drawn in from the Gulf of California and eastern Pacific, and smaller-scale atmospheric disturbances that trigger daily thunderstorm development.

Those local and regional factors tend to matter more than ENSO conditions in the Pacific. Still, El Niño can nudge the broader circulation in ways that sometimes show up at the margins.

In some events, it weakens or shifts the position of the subtropical ridge that helps steer moisture northward into the Desert Southwest. When that happens, parts of Arizona, New Mexico, and far West Texas can see a less organized or more uneven monsoon pattern, with fewer widespread storm days.

But that relationship is not reliable from year to year. Other El Niño summers show near-normal monsoon activity when local heat, moisture availability, and mid-level winds line up in the right way.

In practice, shorter-term weather patterns often overwhelm any ENSO signal during the monsoon season. The more consistent link between El Niño and summer moisture in the broader Southwest comes from tropical activity in the eastern Pacific, which is often more active during El Niño years.

Warmer ocean temperatures and reduced wind shear can support more frequent or stronger tropical systems in that basin. While most storms remain over open water or track away from the U.S., some can send remnant moisture northward into the Southwest.

That can help feed monsoon surges or trigger late-season rainfall events across Arizona and New Mexico, and only rarely extend into Southern California. A developing El Niño in the Pacific Ocean could tilt conditions toward a more active eastern and central Pacific hurricane season this year.

AccuWeather expects 17 to 22 named storms in the Eastern Pacific, along with 9 to 13 hurricanes and 4 to 8 major hurricanes this season. The forecast also calls for 6 to 9 direct impacts to Mexico and Central America, more than double the historical average.

In the Central Pacific, which includes Hawaii, forecasters are calling for 4 to 7 named storms, 2 to 4 hurricanes, and 1 to 3 major hurricanes, with 1 to 2 direct impacts possible for the islands. While California is not typically in the path of tropical systems, forecasters say warmer ocean waters and more favorable storm tracks can increase the risk of tropical moisture reaching the region.

That can translate into heavy rainfall and flash flooding in parts of Southern California, particularly in late-season setups. AccuWeather also warns of an elevated flood risk across the broader Southwest, including Arizona and New Mexico, where remnants of Pacific storms can interact with monsoon moisture and produce intense rainfall far inland.

The Pacific season began on May 15, and hurricane forecasters are already monitoring two possible tropical storms in the eastern Pacific basin, the National Hurricane Center said in a June 1 advisory. El Niño conditions typically suppress Atlantic hurricane activity.

The main driver is increased vertical wind shear, or changes in wind speed and direction with height, which can tear apart developing storms before they organize. El Niño also tends to stabilize the atmosphere over parts of the tropical Atlantic, making it harder for thunderstorms to grow into tropical cyclones.

As a result, El Niño years often bring fewer named storms, a lower chance of major hurricanes, and reduced development from African easterly waves moving off the coast of Africa. While the overall outlook leans below normal, forecasters caution that impact risk remains significant — particularly in seasons where storms form closer to land or undergo rapid intensification.

"People often suffer from a false sense of lead time," said Ken Graham, National Weather Service Director. "Every Category 5 that's made landfall in this country was a tropical storm or less at three days out.

They rapidly intensify and get here quickly. Preparedness early is absolutely key." At the center of the El Niño development is a Kelvin wave — a large pulse of subsurface warm water now rising toward the ocean surface.

A Kelvin wave is a slow-moving pulse of warm water that travels eastward just below the ocean surface along the equator in the Pacific Ocean, according to NOAA. Unlike surface waves that break at the coast, these are subsurface shifts in ocean heat that move across thousands of miles.

They form when changes in wind patterns — especially weaker trade winds or bursts of westerly wind activity — push warm water that has built up in the western Pacific toward the central and eastern Pacific. Kelvin waves generally occur in two phases: a downwelling phase, where warm water is pushed eastward and suppresses colder water from rising to the surface, and an upwelling phase, where colder water from below can rise closer to the surface, temporarily cooling the ocean in some areas.

According to Severe Weather Europe, it is currently in a downwelling phase, meaning it is actively pushing warm subsurface water eastward across the equatorial Pacific and suppressing cooler water from rising to the surface. A single Kelvin wave can take about two to three months to cross the Pacific, giving forecasters an early signal of how ocean temperatures may evolve.

While it does not guarantee an El Niño will develop, strong downwelling waves are often one of the earliest signs that the ocean-atmosphere system is shifting toward warmer conditions.