Wren Crowe 
The disruption makes her happy.
The period from October 2024 to February 2025 witnessed significant meteorological variability across the United States, driven by a combination of La Niña conditions, atmospheric river activity, and dynamic shifts in polar air masses. This report synthesizes temperature anomalies, precipitation trends, and notable weather events during these four months, with a focus on regional impacts and climatic drivers.
Influence of La Niña on Winter Dynamics
Development and Characteristics of La Niña
A weak La Niña emerged in October-December 2024, persisting through January-March 2025, with sea surface temperatures in the central and eastern equatorial Pacific cooling by approximately -0.5°C. This phase reinforced a northward-shifted jet stream, amplifying troughing over the western U.S. and ridging along the southern and eastern states. While weaker than historical La Niña episodes, this event still exerted measurable influence on precipitation distribution and temperature gradients.
Regional Teleconnections
La Niña typically enhances precipitation in the Pacific Northwest and Great Lakes while suppressing rainfall in the Southwest and Southeast. During the 2024-25 winter, these patterns manifested clearly: atmospheric rivers deluged the Northwest, while drought conditions intensified in Texas and the Southern Plains. However, the weak intensity of La Niña contributed to higher-than-expected variability, particularly in the Upper Mississippi River Valley, where temperature and precipitation deviations oscillated between La Niña-like and neutral ENSO conditions.
Temperature Anomalies and Regional Disparities
Persistent Cold in the Northern Tier
From December 2024 through January 2025, the Northern Plains and Great Lakes experienced temperatures 3–5°F below average, with the coldest outbreak occurring between January 20–27, 2025. Arctic air penetrated as far south as the Gulf Coast, triggering rare freezing rain events in Texas and snow accumulations exceeding 6 inches in coastal Alabama. The Pacific Northwest also faced unseasonable chill, with temperatures 2–4°F below normal, aligning with La Niña’s tendency to funnel polar air into the region.
Mild Conditions in the South and East
Contrasting sharply with the North, the southern U.S. remained anomalously warm, with December-February temperatures 4–6°F above average from Texas to the Carolinas. This warmth stemmed from a combination of La Niña-driven ridging and elevated Gulf of Mexico sea surface temperatures, which exceeded historical averages by 1.5°C. Urban centers like Atlanta and Houston recorded their warmest Januarys on record, reducing heating demand but exacerbating drought conditions.
Precipitation and Storm Tracks
Atmospheric Rivers and Western Snowpack
A sequence of atmospheric rivers inundated the West Coast starting in November 2024, with Northern California and the Pacific Northwest receiving 150–200% of average precipitation by February. The Sierra Nevada and Cascades accumulated snowpack at 130% of normal, ensuring robust water reserves for spring. However, a midwinter shift in storm tracks redirected moisture toward Southern California in February, alleviating—but not eliminating—short-term drought concerns in Los Angeles and San Diego.
Eastern Snowstorms and Rain-Snow Line Variability
The Great Lakes and Northeast faced a volatile mix of rain, ice, and snow. Lake-effect snowbands deposited 12–18 inches leeward of Lakes Erie and Ontario during January’s cold outbreaks. Meanwhile, the I-95 corridor oscillated between heavy rain and sleet, with ice storms causing widespread power outages in Pennsylvania and New Jersey. February brought a stark transition, as milder air reduced snow chances east of the Appalachians, though late-month polar vortex disruptions renewed snowfall risks in the Midwest.
Notable Extreme Weather Events
January 2025 Arctic Outbreak
The most severe cold wave of the season occurred January 20–27, 2025, when a lobe of the polar vortex descended into the central U.S. Temperatures plunged to -30°F in North Dakota and -15°F as far south as Oklahoma City. Wind chills below -50°F prompted school closures and emergency declarations across 12 states. Concurrently, a Colorado low-pressure system draped heavy snow from Kansas to Maine, with 18–24 inches reported in Michigan’s Upper Peninsula.
Southern Snowstorm of January 15–17
A rare Gulf low developed off Texas, injecting moisture into subfreezing air entrenched over the Deep South. Mobile, Alabama, received 6.3 inches of snow—the heaviest single-day accumulation since 1985—while Tallahassee, Florida, measured 2.8 inches. The storm disrupted transportation and agriculture, with citrus crop losses exceeding $300 million.
Transition to Milder February Conditions
Rapid Pattern Shift
The final week of January 2025 marked a pivotal transition, as Pacific air masses eroded the eastern cold dome. By February 1, temperatures rebounded 20–30°F above January averages in the Ohio Valley, with Cincinnati rising from -4°F on January 25 to 58°F on February 3. This warmth correlated with a strengthening subtropical jet stream and MJO propagation into the Western Pacific, which dampened La Niña’s influence.
Residual Cold and Late-Season Snow
Despite the overall warming trend, residual cold pockets persisted in the Northwest and northern Rockies. Missoula, Montana, endured February temperatures 5°F below average, and a late-month nor’easter dropped 8–12 inches of snow from Boston to Portland, Maine. Forecast models suggest this variability may presage an extended spring thaw, particularly in the Great Lakes, where ice cover remains 40% below the 2000–2020 median.
