Ag Weather Forum

Weather model guidance is starting to show decent agreement that we'll be headed into La Nina this fall, and it could persist through early 2026.

Ocean temperatures in the east-central tropical Pacific are being monitored closely for the eventual return of La Nina for the second winter in a row. There may be some relief from the drought that's currently expanding in the Eastern Corn Belt during the upcoming winter, but drier and colder conditions could be in store for the Southern Plains to kick off the new year.

The El Nino-Southern Oscillation (ENSO) can be a key to forecasting some of the general weather patterns across North America in the winter season. ENSO is a climate pattern across the tropical Pacific Ocean where meteorologists will monitor sea surface temperatures to see whether they are trending above or below average.

There are two phases to ENSO, with the warm phase named El Nino while the cool phase is La Nina.

When meteorologists monitor sea surface temperatures in the tropical Pacific Ocean, the Nino 3.4 region is often checked for changes. This region extends across the east-central tropical Pacific. During June and early July this year, sea surface temperatures were neither above nor below average. However, through the month of August, temperatures started to dip slightly below average in the Nino 3.4 region as cooler waters from below the surface started to upwell towards the surface of the east-central tropical Pacific.

Model guidance through the rest of September into early October continues to show sea surface temperatures in the Nino 3.4 region dipping below average. Later this fall into early this winter, most models suggest that below-average temperatures will remain in the east-central Pacific, leading to the cool phase of ENSO, La Nina.

Last year, we also saw La Nina develop during the late fall and early winter, but it was a bit delayed at developing. Confidence is higher that La Nina will develop quicker this fall. During a La Nina winter, an area of high pressure will typically dominate the northeast Pacific, and this can cause the polar jet stream to dip farther south over the central U.S.

Cold air outbreaks can be a bit more common as the jet stream will drag cooler air from Canada farther south. Above-average precipitation can also be a side effect of La Nina in the Pacific Northwest and eastern Midwest. Across the southern U.S., warmer and drier conditions are typically favored during a La Nina winter.

Even though we had La Nina arrive late last fall and linger into the winter, it doesn't necessarily mean that the forecast for this fall and winter will look the exact same. DTN's winter outlook for the months of December through February suggests lower temperatures will reside across much of the North with above-average temperatures in the South. February does look slightly different though as a few more cold air outbreaks could spread as far south as the Southern Plains and above-average temperatures will shift to the East.

From a precipitation aspect, DTN is favoring above-average precipitation across the North with drier conditions in the Southern Plains and Southeast. By January, above-average precipitation could be centered across the northern Mississippi Delta into the eastern Midwest, which would be beneficial for increasing water levels along the lower Mississippi and building some of the recently depleted soil moisture in the southeast Corn Belt. February could also end up favoring above-average precipitation in the southeast Corn Belt with drier conditions favored in the Southern Plains.

ENSO and its warm and cold phases are good starting points to predict how the late fall and winter months may pan out for precipitation and temperature trends in North America. However, it is also just one piece to the puzzle when meteorologists predict the weather patterns months in advance. There are many other global weather patterns that can play into the forecast and cause it to deviate from the original forecast. Yet, the timescale to predict many of the other global weather patterns is typically only one or two months in advance. We won't have a better idea for how these will influence the La Nina pattern until we get closer to December.

To find more weather conditions and your local forecast from DTN, head over to https://www.dtnpf.com/….

Teresa Wells can be reached at teresa.wells@dtn.com

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