<p>Frost events can cause severe and often irreversible damage to leaves and canopies. The negative impacts of isolated frost events, defined as discontinuous days of extreme cold, on forests are well documented. However, a critical aspect of frost damage—its prolonged duration—is largely overlooked, even though freezing temperatures often persist for multiple consecutive days in natural environments. The impact of continuous frost events, characterized by consecutive days of extreme cold, on forest growth remains poorly understood. Using multiple remote-sensing data sources, herein we demonstrate that continuous frost events result in significantly greater declines in forest growth compared to isolated frost events across the Northern Hemisphere. Our frost-controlled experiments using seven tree species further confirm that continuous frost causes more severe damage to cell integrity and photosynthetic rate. Using GPP and climate data simulated by CMIP6 models, we find that continuous frost events significantly reduce forest growth by the end of this century, with the largest reductions observed under high-emission scenarios. Our findings underscore the importance of accounting for the prolonged duration of frost events to fully capture their impacts on forest ecosystems, as failing to consider this factor may lead to underestimation of frost-induced effects on forest growth and carbon cycling under climate change.</p>