Farmers in the Midwest may want to pray for more balmy water temperatures off Peru’s equatorial coast. Colder-than-normal seas in this region indicate that a La Niña weather event is still stewing that could negatively alter rainfall and temperature patterns elsewhere, including the U.S. Corn Belt – similar to what occurred during summer 2011.

“The dry-weather bias across the Midwest from August through September last year was, in part, a function of La Niña,” says Drew Lerner, meteorologist and owner, World Weather Inc. “La Niña wasn’t solely responsible for the drought in Indiana and Illinois during early summer last year. However, late in summer, during August and September, La Niña reasserted itself and the drought in Indiana and Illinois spread to other, immediately neighboring states.”

In 2011, spring started out cool and wet in Indiana, with planting delays occurring during April and May, says Shaun Casteel, Purdue University Extension agronomist. “Then, during summer, we experienced drought conditions and a lot of heat stress,” says Casteel. “How the crop performed really came down to how much rain your farm received and when it occurred. In northeastern and southern Indiana, it was fairly common for soybean yields to be only 15, 20 or 30 bu./acre.”

Midwestern crop production could again suffer drought-related yield losses in 2012, depending on what happens with La Niña over the next several months. “The current La Niña is still a weak one, but it is showing some intensification,” says Lerner. “In the Upper Midwest, if La Niña lasts through summer, we’ll likely see good early spring moisture, a decline in precipitation for late spring, heat and dryness beginning to prevail early in summer and then heat and dryness really kicking in during late summer.”

The lingering affects from a devastating drought in Texas last year could also expand any La Niña-related dryness that might occur in the Corn Belt. “The worst case scenario would occur if winter and spring rains are insufficient to break down the Texas drought while dryness remains in the upper Midwest and La Niña remains a significant event through summer,” says Lerner. “In that scenario, dryness would likely extend from Texas to the northern Plains during the corn and soybean growing seasons.”

Extreme weather predictions like this one don’t play out very often, however, he adds. “Frequent rains from Texas into the Midwest (like we’ve seen in December) this winter and spring would help reduce the potential for a worst case of La Niña-induced dryness this summer,” says Lerner. “Easing the dryness in Texas would also help reduce the potential for a significant high pressure ridge to build up in late spring and summer.”

Still, the severity of a La Niña, and how long they last, is hard to predict. Nor do any two La Niña events affect U.S. crop production exactly the same way, due to a complex number of relating factors.

“La Niña’s impact will always be varied, depending on what the prevailing weather pattern is and the intensity of the event itself,” says Lerner. “It’s still too far out to predict how La Niña conditions might impact the 2012 cropping year with any accuracy.”

On occasion, La Niña can actually be good for crop production, he points out. “If the prevailing weather pattern is wet, La Niña will have a positive impact by taking the excess moisture out of the pattern and provide timely rainfall,” says Lerner. “If, however, the prevailing weather pattern is a dry one, La Niña’s influence will be to take away more moisture and the drier-biased pattern will suddenly become too dry – raising concern for crops.”

In just a couple months, meteorologists will be able to more accurately predict La Niña’s impact on Corn Belt agriculture.  “We’ll know a whole lot more about the fate of La Niña in February and March,” says Lerner. “Right now, I expect it to peak in late January or early February, and then to taper off. If that occurs, the bottom line is that crop-growing conditions for corn and soybeans will still be favorable.”