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

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, noted Lerner, who’s with Overland Park, Kan.-based World Weather.

“We can’t make parallels to 1988 with the way things are set up now,” he said at a CME Group crop and weather seminar last week. “There’s not really a connection between an El Nino/La Nina shift and drought. 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 that he uses is predicting a quick transition to La Nina over the next few weeks.

“It will bring changes in global weather patterns, including a possible drier finish” to U.S. weather late this summer and during autumn, he 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 livestock, dairy and poultry 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 USDA data.

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

At today’s market 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 reign. This means a drier bias in August and September and warmer than normal temperatures” in the Midwest.