El Niño is Officially Here. But Eric Snodgrass Says Don’t Expect It to Drive Summer Weather

NOAA officially declared El Niño has developed in the tropical Pacific on Thursday, but the bigger headline for agriculture this summer may not be the evolving weather pattern. Instead, one ag meteorologist says there are bigger factors to watch this summer.

The agency’s National Weather Service says El Niño is expected to strengthen through the fall, with forecasters assigning a 63% chance that sea surface temperatures in the monitored Niño region exceed 2.0°C above average later this year. If that threshold is reached, NOAA would classify the event as a “very strong” El Niño, putting it among some of the most significant events on record.

(NOAA )

While the declaration is making headlines now, meteorologists have been watching the signal build for months.

“NOAA has its own specific set of rules by which they declare El Niños and La Niñas, and they adhere to those rules, which is important,” says Eric Snodgrass, senior science fellow with Nutrien Ag Solutions. “Many of us in meteorology sometimes want to jump the gun in spring and say, ‘Oh no, it’s going to happen.’ But we have a well-known thing in meteorology called the spring forecast barrier. What NOAA does is they wait until they get past that to give us the prediction.”

Snodgrass says what’s unfolding in the Pacific has been extraordinary.

“We’ve been watching the ocean temperatures change rapidly since February,” he says. “It’s actually the fastest development from La Niña to El Niño we have on record. Technically, if you look at the trade wind behavior and the ocean temperatures right now in the equatorial Pacific, we’re already in what we would consider a moderate El Niño. And it’s only going to get stronger from here and potentially become a historic event by the time we get into fall.”

Summer Weather Still Hinges on Other Factors

Even with NOAA’s declaration, Snodgrass says farmers shouldn’t assume El Niño will be the primary driver of weather during the heart of the growing season.

“Historically, the correlations with El Niño and summer weather patterns are weak. It’s not as strong as we’d like,” he says. “I wish it was the most dominant factor in summer because then I’d be really good at my job. But the reality is summer is defined by thunderstorm complexes. It’s defined by very weak boundaries. It’s defined by heat. As a result, predicting it days and weeks in advance is difficult.”

Instead, Snodgrass says producers should continue monitoring factors that have stronger correlations to summer weather.

“Ocean temperatures off the West Coast are huge,” he explains. “The colder they get, the hotter the temperatures get in the Midwest. There’s a pretty strong relationship there. The other piece is if you’re trying to predict July heat, you want to look at June soil moisture. If by the end of the month we have good moisture throughout much of the Midwest, Mid-South and even the Southern Plains, then we tend to back away from the risk of heat.”

He cautions that summer forecasts can change quickly if atmospheric patterns shift.

“You can have all the great forecasting graphics in the world and see all these little relationships, but if you get the wrong pattern showing up at the wrong time, all of a sudden the momentum drops off, a big ridge builds in and we have all sorts of heat and drought problems,” he says. “The plant responds very, very quickly to that. Right now we’re saying the odds of that happening are limited, but our most important forecast comes in the last week of June. That’s when we start to see all the pieces come together and we’ll know how July is going to play out.”

(Eric Snodgrass)

That outlook comes as parts of the Midwest continue to battle excessive rainfall. Snodgrass notes portions of eastern Kansas through northern Missouri have received significant precipitation in recent days, with some locations seeing as much as nine inches of rain.

“We had a big storm,” he says. “I just got an email from a producer this morning who said, ‘We are underwater and this crop is going to be a problem.’ In those areas, lack of oxygen in the root zone becomes a concern. Meanwhile, there are other places, like much of Illinois, that received just the right amount of rain.”

El Niño’s Bigger Influence Arrives This Fall

While its impact on summer weather may be limited, Snodgrass says El Niño is likely to become the dominant weather driver as the calendar moves toward harvest and winter.

“Come fall during hurricane season and then getting into winter, it will be the most dominant factor predicting this upcoming fall and winter,” he says.

That could bring a different weather pattern than farmers have experienced in recent years.

“We have seen multiple falls in a row of very, very dry conditions,” Snodgrass says. “The Mississippi River has gone way down. We’ve had trouble getting barge traffic up and down that river. We’ve had long harvest periods, but we’ve also had difficulty because the ground has become so very hard. This fall, there’s a better chance that conditions are near normal or even wetter than normal, especially in the southern tier of the United States.”

According to NOAA, a typical El Niño winter shifts the Pacific jet stream southward, increasing the likelihood of stormier weather across the southern United States while often producing warmer-than-normal temperatures across the northern tier of the country. El Niño can also suppress Atlantic hurricane activity by increasing upper-level winds that disrupt tropical storm development.

Looking Back at Historic Comparisons

If NOAA’s forecast for a strong or very strong El Niño materializes, Snodgrass says the closest comparisons may be some of the most memorable events of the past several decades.

“I think we’re going to have to go back and compare this to those big years like 1997 and 2015 for a good forecast for the upcoming fall,” he says. “We had an El Niño in 2023, but this one has the potential to be much more significant.”

Still, NOAA officials caution that every event has its own unique fingerprint.

“Every El Niño is not the same; each one is unique with its own imprint on our weather,” says Ken Graham, director of NOAA’s National Weather Service.

For farmers, that means the official declaration offers an important clue about weather risks and opportunities later this year. But for the next several weeks, crop conditions will likely be determined by more localized weather patterns than by the warming waters of the equatorial Pacific.

What a Strong El Niño Could Mean for U.S. Weather

While El Niño’s influence on summer weather is often limited, its impacts tend to become much more pronounced during the fall and winter months.

According to NOAA, a typical El Niño pattern shifts the Pacific jet stream farther south, steering more storms across the southern tier of the United States. That often results in wetter conditions across portions of the South, while areas such as the Northern Rockies and parts of the Ohio and Tennessee valleys can trend drier than normal. Temperatures across much of the northern U.S. also tend to run warmer than average during El Niño winters.

“Every El Niño is not the same; each one is unique with its own imprint on our weather,” says Ken Graham, director of NOAA’s National Weather Service. “Advanced monitoring and an improved understanding of El Niño patterns allow the NWS to better predict and better prepare the public and our core partners for what is to come.”

Beyond precipitation and temperature trends, El Niño can also influence hurricane activity. Stronger upper-level winds associated with the pattern often suppress storm development in the Atlantic Basin while increasing opportunities for tropical development in portions of the Pacific Ocean.

NOAA says a stronger El Niño can also raise the risk of high-tide flooding along parts of the West Coast and affect ocean ecosystems by altering fish migration patterns and increasing the likelihood of harmful algal blooms.

For agriculture, however, the most closely watched impacts are often tied to precipitation. With several consecutive dry falls affecting river levels, harvest conditions and transportation, a stronger El Niño could increase the odds of more active storm systems and improved moisture across portions of the southern United States later this year.