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La Niña, the coldest phase of the El Niño-Southern Oscillation (ENSO) cycle, officially emerged in September 2025, with below-average sea surface temperatures in the central and eastern equatorial Pacific Ocean.
As of mid-October 2025, it remained weak (with anomalies between -0.5°C and -0.8°C in the Niño 3.4 region) and is projected to persist at least from December 2025 to February 2026, although it could reach neutral conditions by early 2026.
This phenomenon marks the fifth La Niña event in six years, contributing to prolonged patterns of global climate variability.
In the Atlantic hurricane season (June 1 to November 30), La Niña’s late arrival means that its influence is primarily felt late in the season, including the second half of October.
La Niña typically intensifies Atlantic hurricane activity by reducing vertical wind shear (changes in wind speed with altitude) over the tropical Atlantic, the Caribbean, and the Gulf of Mexico.
This facilitates storm formation and intensification, especially in the deep tropics. Above-average Atlantic sea surface temperatures (despite some early-season cooling due to an unrelated “Atlantic La Niña” pattern) further increase this potential.
Forecasts from NOAA, Colorado State University (CSU), and AccuWeather predicted a slightly above-normal hurricane season for 2025 (17 named storms, 9 hurricanes, and 4 major hurricanes).
However, activity has been below average to date, with only 10 named storms and 4 hurricanes in early October, due to high wind shear and dry air intrusions early in the season.
The emergence of La Niña has not yet reversed this quiet start, but is shifting conditions toward more favorable development.
Specific to the second half of October 2025: This period coincides with the climatological peak of activity at the end of the season.
The reduced shear under La Niña favors storms originating from African easterlies, increasing risks in the Caribbean and Gulf.
As of October 21, models show a low pressure area (98L) off Africa with a 20-30% chance of becoming a tropical depression by late October, potentially the eleventh named storm.
CSU notes lower confidence in the overall forecast due to this variability, but historical analogs (e.g., 2000, 2016) suggest a more active season, with the possibility of one or two additional systems between October and November.
Consequences for Climate, Society, and the Environment
While the weak nature of La Niña moderates some extremes, its timing amplifies risks at the end of the hurricane season. The consequences extend beyond storms and affect broader weather patterns:
According to NOAA, activity in November doubled compared to neutral or El Niño years. Late October could see rapid intensification driven by warming waters (e.g., Gulf sea surface temperatures (SSTs) >28°C), increasing the risk of flooding, storm surge, and wind damage.
Higher likelihood of occurrence along the U.S. Gulf Coast (e.g., Louisiana, Florida) and the Carolinas; the Caribbean islands face a heightened risk of major hurricanes.
The early-season lull has bred complacency, but experts warn of the possibility of non-impact cyclones ending abruptly.
Possible damages of $10 billion to $50 billion from a single major hurricane making landfall (based on 2020-2024 analogs). Evacuations, power outages, and supply chain disruptions could affect 10 million to 20 million people in coastal areas.
US Fall/Winter Outlook: Drier and warmer conditions in the southern US (e.g., droughts in Florida and wildfires like those in 2017); wetter and cooler conditions in the Pacific Northwest and northern Plains.
Globally, typhoons intensified in the Pacific, but Indian Ocean monsoons were suppressed.
Coral bleaching due to persistent warm Atlantic waters; Disruption of marine ecosystems. In agriculture, a drier Southeast could negatively impact crops, while northern rains boost production in the Midwest.
Despite the cooling La Niña, 2025 temperatures will remain above average due to anthropogenic warming, exacerbating heat waves and hampering recovery from previous El Niño floods.
No major hurricane has yet hit the U.S. in 2025, but La Niña’s weakness has allowed volatile patterns to keep early threats at bay, providing a brief “nap” before potential late waves.
The weak and late start of the 2025 La Niña has disappointed expectations of a hyperactive hurricane season, resulting in below-average activity to date.
However, its persistence until late October introduces an unpredictable factor: a wave of storms in the Gulf/Caribbean that could end the season on a destructive note, similar to those of 2020 and 2022.
With only approximately 12% of the season climatologically remaining, vigilance is essential: preparation (e.g., stockpiling supplies, monitoring NHC updates) compensates for the low immediate probabilities.
In the long term, this event underscores ENSO’s role in exacerbating climate change: even mild La Niñas amplify extremes in a context of global warming. By 2026, a possible repeat raises concerns about consecutive active seasons.
Stakeholders should prioritize resilient infrastructure, early warnings, and adaptive agriculture to mitigate cascading risks.
As Brian Tang of the University at Albany points out, the reduced shear caused by La Niña “allows for more and larger storms, especially later in the year,” reminding us that the season “ain’t over until it’s over.”
