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scientific study published early this year has shown how solar eclipses over land can alter the development of clouds. The Moon’s shadow in a solar eclipse results in rapid cooling of the ground surface as it passes over. This cooling, the study found, is enough to hinder or even halt the development of thermals, the invisible columns of air that usually rise from the warmed ground and form Cumulus clouds. As a result, low-altitude Cumulus clouds quickly disappear during an eclipse and new ones are prevented from forming.Although cloud formation returns to normal as the shadow moves on, the sudden shift in cloud cover may affect local weather and precipitation patterns later in the day of the eclipse. Less cloud cover means more solar radiation reaches the Earth because low clouds reflect away much of the Sun’s heat. The potentially affected area can be large, as you can see from this image by NASA’s Earth Polychromatic Imaging Camera (EPIC) aboard NOAA’s Deep Space Climate Observatory in which the Moon’s shadow during the 2017 solar eclipse covers most of North America. Given how an eclipse seems to mess with the conditions, weather forecasters might want to take the day off on an eclipse day – to sit outside and enjoy the spectacle instead.The study referred to here is Trees, VJH; de Roode, SR; Wiltink, JI et al. ‘Clouds dissipate quickly during solar eclipses as the land surface cools’ in Communications Earth & Environment 5, 71 (2024).