A favorable North American weather pattern of warmer central Pacific Ocean waters, also known as an El Niño, is poised to return after several years’ absence.

That’s good news for many farmers. For California growers, many suffering through at least a third consecutive year of drought, El Niño could bring rain. That’s likely for Southwestern farmers, too, says Mike Halpert, acting director of the U.S. Climate Prediction Center.

In the Midwest, wet fields probably won’t turn as dry as they have the past three of four years of an “extreme La Niña-controlled environment,” predicted Elwynn Taylor, Iowa State University Extension climatologist, at Hay & Forage Expo in Boone, IA, last week (see "Hay Expo Weather Report").

Those growers can expect good hay harvests and trendline or above corn yields as an El Niño moves in, he says.

But an El Niño may not be a silver bullet, particularly in areas currently hit by drought, suggests Laura Edwards, climate field specialist with South Dakota State University Extension.

Typically occurring every three to seven years, an El Niño usually results in a mild Atlantic hurricane season, moderate winter temperatures in the North and rain in many dry states. A La Niña is just the opposite, bringing cooler temperatures and dry weather, particularly to the Southwestern U.S.

Climate experts issued an El Niño watch in March after temperatures under the ocean’s surface rose significantly. At that time, temperatures rivaled those experienced in 1997, when a strong El Niño brought needed rains to many ag areas.

Computer models put the likelihood of a new El Niño at 70% or more, says Halpert. Some experts expect the weather phenomenon to develop sometime within the next six months.

But Taylor exuded more confidence. “El Niño is at our doorstep right now,” he said. “It has to be in the middle of the Pacific Ocean before it starts affecting us. I suspect that will be before August is over. Maybe it will have enough of an effect here that we won’t have the same thing happening that happened to us for years when it went from very wet to very dry. That’s typical when you are still under control of La Niña, at least to some extent, but that control is slipping now.”

What's unknown is how strong the El Niño will be, Halpert says. During its 1997 appearance, ocean temperatures continued to rise through spring and summer. This year, temperatures have not continued to warm.

“Right now, conditions across the Pacific have been pretty flat,” he says. The Climate Prediction Center’s next El Niño update will be released July 10. That report will help the center determine if the current El Niño watch should be upgraded to an advisory.

 “An El Niño this year that produced a surplus of rainfall in California and Texas, I think, would be looked at as a good thing,” Halpert says. “Even if it turns out to be too much rain, it’s still better than another year of drought.”

An average El Niño lasts between nine to 12 months; how it will effect ag production is anybody’s guess, he says.

The variability of each El Niño makes it difficult to know what the eventual impact on agriculture will be across the U.S., agrees Edwards.

“The indicators in the Pacific are pretty strong, but that doesn't always translate into how much rain California gets or how cold it gets in the Upper Midwest,” she says. “El Niño may not be the drought-buster that people are hoping for. You can’t always hang your hat on El Niño making a difference.”

As for producers in the Midwest, whether an El Niño is helpful or not depends on the timing, Edwards says. If it develops at the end of the growing season, the favorable weather may not make a difference, she surmises.

Iowa State’s Taylor, however, reassured Hay & Forage Expo attendees that good weather was ahead.

“As we move into an El Niño, (we can expect) generally mild weather in the Midwest, the extremes clipped off both of the cold end and the hot end, the wet end and the dry end,” he said.

This coming winter won’t be as harsh as was the past winter thanks to the movement towards an El Niño, he added.

“But, overall, I think we are moving into a harsh cycle of winters, the harsh years harsher and the mild years not quite as mild over the next 20 years compared to the past 20 years here in the Midwest.”

Contact Halpert at 301-683-3427 or mike.halpert@noaa.gov, and Edwards at 605-626-2870 or laura.edwards@sdstate.edu. Follow Taylor on Twitter.