Heat dome and high pressure boost southern US solar as polar vortex clouds the north

In a recent weekly update for PV Magazine, Solcast, a DNV company, has highlighted a stark solar divide that unfolded across North America last month. The continent experienced a pronounced contrast in solar conditions, with southern regions such as northeastern Mexico, southeastern Texas, and much of California recording 20–25% above-average irradiance, while Canada, the Great Lakes, and the northeastern United States faced persistent cloudiness and below-normal solar conditions. This dramatic difference was driven by distinct meteorological patterns in the north and south, with high-pressure systems and a southwestern heat dome in the south contributing to clear skies and enhanced solar resource, and a polar vortex bringing cold air and storms to the north.

The analysis, conducted using the Solcast API, revealed that the southern half of North America experienced widespread increases in solar resource during the month, while the north faced persistent cloud and storm activity. The strongest gains were centered on northeastern Mexico and southeastern Texas, where deviations reached roughly 20–25% above the long-term March average. Much of California also saw similar increases, benefiting from the same meteorological conditions that enhanced solar irradiance further south.

In contrast, Canada, the Great Lakes, and the northeastern United States recorded lower-than-normal irradiance as polar air and storm systems dominated conditions. This produced a month in which the usual seasonal contrast between north and south was sharpened, with clearer skies in the south and cloudier conditions in the north compared with the 2007–2025 average.

Much of the southern United States and northern Mexico benefited from a pair of high-pressure systems positioned over the Pacific and Atlantic coasts of North America. These systems stabilized the atmosphere, keeping skies clearer than normal across large areas. The high-pressure systems contributed to a heat dome over the southwestern United States, further reinforcing these conditions and driving temperatures 10–19°C (18-35°F) above seasonal norms. This heat dome broke multiple records and created an environment that was highly conducive to solar energy generation.

However, not all regions in the south experienced the same level of solar benefits. Southern Mexico and Florida were exceptions to the southern trend, each experiencing slightly below-average irradiance due to localized cloud cover that persisted in these areas. Despite this, the overall impact of the high-pressure systems and heat dome was significant, leading to a marked increase in solar resource across much of the southern United States and northern Mexico.

The polar vortex, on the other hand, brought cold air and storms to the north, resulting in persistent cloudiness and below-normal solar conditions. This meteorological phenomenon disrupted the typical seasonal patterns, leading to a more pronounced divide between the north and south. The combination of high-pressure systems in the south and the polar vortex in the north created a stark contrast in solar irradiance, with the south benefiting from clearer skies and the north facing cloudier conditions.

In conclusion, the solar divide that unfolded across North America last month was a direct result of the interaction between high-pressure systems and a southwestern heat dome in the south, and a polar vortex bringing cold air and storms to the north. This meteorological contrast led to significant differences in solar irradiance, with the south experiencing above-average conditions and the north facing below-normal solar resource. As the climate continues to evolve, understanding these patterns and their impact on solar energy generation will become increasingly important for both energy planners and consumers.