Midwest farmers and livestock producers face warmer and drier than normal weather later this summer as a La Nina effect takes hold, agricultural meteorologist Drew Lerner said.

While La Nina has been associated with U.S. droughts in previous years, any widespread, severe dryness similar to what happened in 1988 is unlikely, said Lerner, who’s with Overland Park, Kan.-based World Weather, Inc.

“We can’t make parallels to 1988 with the way things are set up now,” Lerner said last week during a crop and weather seminar hosted by CME Group, the Chicago futures exchange operator.

“There’s not really a connection between an El Nino-La Nina shift and drought,” Lerner said. “Just because you have a La Nina doesn’t mean you’re going to have a big, bad drought.”

La Nina is the cooling of surface waters off the western coast of South America that inhibits the formation of rain-producing clouds. Like its counterpart, El Nino, La Nina affects weather patterns worldwide, sometimes leading to extreme conditions.

Sea surface temperatures in the eastern Pacific are rapidly cooling, suggesting La Nina is evolving now, Lerner said. A model used by Lerner predicts a quick transition to La Nina over the next few weeks, he said.

“The change will bring changes in global weather patterns, including a possible drier finish” to U.S. weather late this summer and during autumn, Lerner said. “We won’t have a drought of huge proportions this year. We will have some areas of dryness that will affect crops.”

Midwest weather over the next three months isn’t expected to pose a major threat to corn and soybean crops, suggesting ample feed supplies for beef, pork and dairy producers.

U.S. farmers planted corn ahead of schedule this spring, seeding the third-largest corn acreage total since the end of World War II, according to U.S. Department of Agriculture data.

Also, the corn crop is mostly in strong condition. As of June 27, 73 percent of the corn crop was rated “good” or “excellent,” according to the USDA.

At today’s close, December corn futures in Chicago fell 4 ¾ cents to $3.79 ¾ a bushel.

Still, Lerner expects a “moderately strong” La Nina in 2010 that should last over a year, and potentially have a “huge” impact. “Keep an eye on 2011” weather, he added.

“La Nina will be king,” Lerner said. “This means a drier bias in August and September and warmer than normal temperatures” in the Midwest.