Ag Weather Forum
Weather Outlook Through Summer 2025 Sees La Nina Losing Influence During Spring
This year is tough on long-range forecasters looking at the heart of the 2025 growing season in the United States. During the previous four years, a major force in the Pacific Ocean's El Nino Southern Oscillation (ENSO) Index was in play and the trajectory of those features were a relatively known quantity. While the actual weather didn't follow the forecast exactly in each of those years, the evidence was there to make a confident forecast for the seasons ahead.
This year is a little different.
La Nina is weak and is not forecast to last long into spring. A typical La Nina pattern of colder north and warm and dry south is expected for late winter and could continue into spring, causing slower-than-normal rises in soil temperatures.
Extreme wetness may be an issue in the Ohio Valley, as well. Both may cause planting delays in some areas. When we get to summer, the lack of a strong ENSO force will mean variable and perhaps unpredictable weather conditions.
While good weather conditions are for now forecast for this growing season, a look at history suggests we will probably see some hot and dry conditions entrenched in some areas and could target the middle of the country.
LA NINA MAKING A BRIEF APPEARANCE
It starts with the cold side of ENSO, La Nina, and its reluctance to appear until January 2025. Some forecasts were calling for it to begin as early as June 2024, but it held off. The Climate Prediction Center, a division of NOAA, recently declared that waters in the tropical Pacific Ocean were cold enough, the atmosphere was showing increased easterly winds, and this pattern was forecast to continue long enough (during the next three months) to make this a true La Nina. However, forecasters in the agency also expect that this will be a brief visit of the cold event. (https://www.cpc.ncep.noaa.gov/…)
Model forecasts from around the world have water temperatures rising above the La Nina threshold of 0.5 degrees Celsius below normal by the end of spring, thus ending the event after about four or five months. Many of the global climate models keep ocean temperatures below normal through the summer and into the fall 2025 season, but technically in the neutral state. That is yet to be determined, and another La Nina may develop this coming fall.
But for the next several weeks, we should see La Nina peaking and then gradually diminishing in both its strength and influence on the atmosphere going into summer.
With ENSO conditions becoming neutral again, we will not have our big climate driver through much of the growing season. Smaller, more volatile impacts to our global weather system will matter more and may take control at various points in the year. They are also less predictable, at least beyond the period of about a month. Therefore, the extended seasonal forecast does have some unpredictability to it and will make for some low-confidence forecasts.
In such cases, we at DTN like to use analogs, or years in the past that look similar to what we expect for the future. We take into account ENSO and other weather drivers, especially the other world oceans, to give us an idea of the conditions that may present themselves during the course of the season. We do our best to match previous years to the current one and the forecast during the next couple of months to give us a baseline for what to expect over a longer period. We then blend that with computer models and our expert experience to produce the forecast and give the below insights.
Though we hope the forecast turns out as described below, we know that there will be some errors embedded in them. Even years that may look exactly like we have seen during the previous two months will turn out to be different because every year is different. Also, be aware that seasonal forecasts are not the same as a daily forecast. We cannot predict the exact day you will see rain, how many days you will have between rains, or the exact temperatures during the most critical time for your crops. Even a warm and dry month will have days where it is cooler with rain.
But we can offer ideas on the general concerns or lack thereof for the seasons ahead and hope to give you an idea of what you might expect, allowing you to plan your farm's potential needs and marketing decisions.
REST OF WINTER FORECAST
January has displayed a La Nina type of look, though only slightly. La Nina typically leads to a weakened and amplified jet stream over North America during the winter. This usually results in warmer and drier conditions over the south and colder conditions across the north. Areas that typically benefit from increased precipitation are over the Pacific Northwest and across the Ohio Valley.
While the pattern has been active recently across the middle of the country, cold weather has been more aggressive at penetrating deeper throughout the country. This has led to increased precipitation farther south than we typically see during La Nina as well.
That may be changing for the end of January and into February. The jet stream seems to be adjusting, moving more toward a typical La Nina pattern. That involves an upper-level ridge in the Pacific up through Alaska, and a trough across Western Canada into the Northern Plains. At the same time, a ridge developing over the Southeast will cause temperatures to rise and open up the Gulf of Mexico a bit for storms to use.
Thus, the storm track should lie between the two features, causing more winter storms to move from the Plains through the Midwest, and could bump up some snowfall across the northern tier where it has been lacking so far this year.
HOW WILL LA NINA END IN THE SPRING?
La Nina is forecast to gradually dissipate in the spring and its influence could linger through the middle of the season. Lower temperatures may stick around longer, or we may see bursts of colder air longer into the spring than we usually see. That could cause some areas of the country to see soil temperatures rise more slowly. If substantial snow cover exists across the north, that could delay fieldwork as well, as it sticks around longer than its welcome and would be slower to drain away.
But these areas in the north need the snowpack this year. Substantial drought set in during the fall and has not been able to be reduced during the first half of winter. A lack of a snowpack could lead to soil moisture concerns for sowing seeds and greening forages. Areas that would tend to benefit from this pattern would be in the Ohio Valley, with an extended winter season and wet spring that should lead to good soil moisture for germination and early growth. However, that could also have major concerns if it is too wet this spring. We have seen these types of scenarios follow in recent years where spring planting is delayed because of substantially wet soils.
One final concern could be late frosts. The insistence of cold lingering later in the spring would lead to more concerns that a cold period produces frosts. That of course would be more of a concern for northern areas. But even the Southern Plains, which sees winter wheat growing vigorously in April, may be more under the gun for a late frost.
UNCERTAINTIES ABOUND FOR SUMMER FORECAST
After the crops get planted in the spring, the attention will turn to heat stress and drought concerns for the summer and there are some major concerns here as well. Though ENSO is expected to be in a neutral state, the side of neutral it is on, either warm or cold, will matter. The colder ENSO is, the more likely we see a hot and dry summer across the middle of the country. A warmer ENSO would give more variability to the weather patterns, thus allowing for more seasonal rainfall, much like we saw in 2024.
Forecasts from most global climate models are forecasting ENSO to be on the cool side of neutral, meaning a greater likelihood of some hotter and drier weather during the summer.
The DTN forecast also looks at some of these analog years coming off of a weak La Nina and into cool-neutral ENSO conditions. Years like 2001, 2006 and 2018 are high on our list. During those summers, a pronounced above-normal temperature signature was present over a great deal of territory. However, it wasn't completely dry. Two of those years, 2001 and 2006, showed a lot more variability in the rainfall patterns across the country, especially in the Corn Belt. 2018 was actually a fairly wet year in many areas of the country. So, there is some hope.
Models, which are hard to trust at that range, show a much drier pattern though, and so DTN's forecast does lean toward the drier end, especially in the Plains and western half of the Corn Belt. However, in talking with the long-range forecast team here at DTN, they aren't very confident in the summer forecast. "You never are when ENSO is neutral," said DTN Senior Long-Range Weather Risk Communicator Nathan Hamblin. "Sub-seasonal factors will matter more and those are impossible to predict at this range."
It looks like summer will yet again come down to the haves and have-nots. While DTN expects to see some variability, and thus some areas to see good weather conditions this growing season, there are bound to be areas that see a worse combination of heat and drought to cause concern.
And those areas may be large. Hamblin said that areas across the north seem to have more of a risk at this time. "There are concerns, especially in the Northern Plains where drought currently exists, and across the Upper Midwest, where there is some tendency in our analog package for drier weather in the summer."
To find more weather conditions and your local forecast from DTN, head over to https://www.dtnpf.com/…
John Baranick can be reached at john.baranick@dtn.com
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