<p>Rapidly intensifying flash droughts during the growing season pose a critical threat to global food security. However, how their impacts on crop yields differ from traditional slow-onset droughts and the underlying mechanisms remain inadequately quantified. Here, by integrating long-term yield records, phenological observations, and reanalysis datasets, we show that flash droughts cause widespread maize yield losses across the United States, with a yield sensitivity 27.53% (19.85–36.53%) greater than that of slow-onset droughts. We further demonstrate that this amplified sensitivity is primarily associated with intensified atmospheric aridity during flash droughts, particularly when flash drought development coincides with critical phenological stages. Yet most process-based crop models systematically underestimate this yield sensitivity, likely due to their insufficient representation of rapid soil moisture depletion. Although irrigation can partially mitigate yield losses, it remains unable to fully buffer crops from flash droughts. Our findings underscore the need to improve crop model fidelity and develop targeted strategies for agricultural resilience against flash droughts.</p>