The El Niño-Southern Oscillation (ENSO) is a well-known climate phenomenon that brings significant shifts in sea surface temperatures, ocean currents, and atmospheric conditions in the tropical Pacific Ocean.
ENSO manifests in three distinct phases: neutral, La Niña, and El Niño, each influencing weather patterns across the contiguous United States in unique ways.
Current forecasts suggest that La Niña conditions are likely to persist from September 2025 through January 2026, with the National Oceanic and Atmospheric Administration (NOAA) indicating a greater than 50% chance for La Niña during this period.
The anticipated impacts of La Niña are critical, particularly concerning precipitation and temperature trends, which are expected to contribute to drought conditions across various regions.
La Niña generally leads to below-average precipitation and above-average temperatures in the Southern U.S. during the cool seasons, while the Northern U.S. sees the opposite effects.
In particular, the Southwest United States, including states like California, Nevada, Arizona, and Utah, will likely experience persistent drought conditions facilitated by La Niña.
This is due to a higher chance of below-average precipitation, a trend that may extend to the Southeast region as well as parts of Texas, New Mexico, and Oklahoma.
While La Niña increases the likelihood of drought in the South, it contrasts significantly with the weather expectations for the Northern U.S.
During this same period, the Pacific Northwest, Intermountain West, and Ohio Valley can expect above-average precipitation, which may lead to drought improvement in these areas.
To monitor ENSO, NOAA utilizes the Oceanic Niño Index (ONI), which taps into three-month running averages of sea surface temperature deviations from the norm in the Niño3.4 region.
El Niño events are identified when the ONI exceeds 0.5°C for five consecutive three-month periods, while La Niña events are classified when values fall below -0.5°C for the same duration.
The historical data shows a periodic occurrence of both El Niño and La Niña events, with several recorded each decade from 1950 to 2025.
The effects of these weather patterns notably influence the onset, persistence, and termination of drought conditions across the contiguous United States.
Specifically, during the cool seasons, La Niña is associated with significantly increased chances of dry conditions in the Southwest, impacting water resources and agriculture.
Conversely, the Northern U.S. is more prone to favorable precipitation and lower temperatures, particularly during September through May.
As late 2025 approaches and forecasts confirm the likelihood of La Niña, concerns about drought in the Southwestern region will intensify.
The forecast emphasizes the need for increased awareness and preparation for potential drought conditions, particularly with the backdrop of current drought situations that have developed.
NOAA’s probabilistic ENSO forecast indicates a sustained La Niña presence across late 2025 and early 2026, projecting extensive influences on the weather that will affect millions across the country.
While the outlook may seem dire for the Southwest, it’s important to note that the impacts of La Niña can vary from one event to another.
For example, the previous La Niña conditions experienced in 2024-2025 did not bring uniform effects; some areas in the Northwest received above-normal precipitation, but these benefits were short-lived as conditions dried out quickly during the subsequent spring and summer.
As we look toward the future, the National Integrated Drought Information System (NIDIS) and its partners are poised to continue monitoring ENSO developments and provide regular updates on climate influences throughout the upcoming water year.
With preparations underway, regions across the United States will need to be vigilant in managing water resources and mitigating the effects of potential drought brought on by the La Niña conditions anticipated over the coming months.
In summary, the forecasted La Niña conditions raise significant concerns for drought in late 2025 and early 2026, predominantly in the Southwest, while offering some relief in the Northwest.
Monitoring and adaptive strategies will be essential as these patterns unfold, impacting not only weather but also agriculture, water management, and overall climate resilience in affected regions.
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