Winter weather splits solar conditions across North America

In a new weekly update for pv magazine, Solcast, a DNV company, reports that destabilized polar circulation in February produced wet and cloudy conditions in some parts of North America, while the central and eastern regions enjoyed elevated irradiance under clearer conditions.

March 6, 2026 Solcast

Image: Solcast

From pv magazine Global

A combination of stratospheric warming and a disrupted polar vortex produced sharply contrasting irradiance patterns across North America in February, according to analysis using the Solcast API. The destabilized polar circulation produced wetter and cloudier conditions in parts of the north while keeping the central and eastern regions under clearer conditions and elevated irradiance. These opposing patterns created a clear divide in solar performance across the continent, with several inland grids experiencing stronger than normal conditions while coastal regions saw suppressed irradiance.

A major driver of this pattern was stratospheric warming – a rapid warming of the upper atmosphere that disrupts the polar vortex which weakened and disrupted northern circulation patterns during February. This disruption allowed the jet stream to develop waves, shifting storm tracks and cloud distribution across North America. The resulting circulation pattern supported higher irradiance across large portions of the United States despite ongoing winter weather in some regions. Western areas experienced reduced solar resource due to unsettled conditions, while the central and eastern United States saw clearer skies and higher irradiance anomalies.

Opportunities were particularly strong across the ERCOT and ISO-NE grids, where irradiance increases approached 20% alongside unusually high temperatures exceeding 38°C (100° F) in some locations. Even a late-month nor’easter or winter storm that brought heavy snow to the northeastern United States did not significantly reduce the broader pattern of elevated solar conditions. Above-average irradiance extended beyond the United States, reaching from the Rio Grande across east coast of Mexico and southern Quebec.

Despite widespread inland improvements, several coastal regions experienced reduced solar resource due to anomalous weather systems. North and South Carolina recorded around a 15% reduction in irradiance during February as snow and ice events increased cloud cover. Northern California saw similar reductions as a series of atmospheric rivers brought persistent cloudiness and precipitation, suppressing irradiance across the CAISO region. The Appalachian Mountain chain formed a clear boundary between regions of increased and reduced irradiance conditions along parts of the eastern seaboard.

February also marked a step-change in solar conditions compared to January. Across much of the Central and Eastern United States, irradiance patterns supported double-digit solar overperformance, with increases of around 15% to 25% relative to typical February levels. ERCOT stood out within this pattern, where parts of Texas experienced exceptional solar conditions — longer days and seasonal improvements compounded with unusually clear skies to drive irradiance around 25% above seasonal norms, and +40% above January levels, as seen in Dallas, TX.

Solcast produces these figures by tracking clouds and aerosols at 1-2km resolution globally, using satellite data and proprietary AI/ML algorithms. This data is used to drive irradiance models, enabling Solcast to calculate irradiance at high resolution, with typical bias of less than 2%, and also cloud-tracking forecasts. This data is used by more than 350 companies managing over 300 GW of solar assets globally.

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