Spatio-temporal evolution of late spring frost and associated yield reduction risk for winter wheat in China

Late spring frost remains a major threat to winter wheat even as the climate warms, because accelerated crop development can increase the overlap between frost-sensitive stages and episodic spring cold events. Yet large-scale yield risk remains difficult to quantify because this overlap changes over time and frost damage differs among cultivars. We developed a phenology-constrained, event-based framework that integrates controlled low-temperature experiments, phenology reconstruction constrained by agrometeorological observations, machine-learning-based yield-reduction modelling, and bias-corrected hourly temperature projections. We assessed three cultivar resistance groups across China’s major winter wheat regions during 1980–2024 and under SSP2–4.5 and SSP5–8.5 during 2030–2100. Warming did not uniformly reduce frost damage but shifted its geographic center. For cold-sensitive cultivars, historical mean yield reduction was greatest in the Middle–Lower Reaches of the Yangtze River region (10.02%), whereas the Huang–Huai region became the principal future hotspot, reaching 6.49% under SSP5–8.5. This redistribution arose from phenological advancement and changes in the frequency and persistence of cold exposure during sensitive stages, while changes in minimum temperature were comparatively small. Counterfactual simulations using fixed historical phenology showed that dynamic phenological shifts increased future losses, mainly during jointing, the stage that dominated losses across both periods. Cold-tolerant cultivars reduced losses by approximately half in the most vulnerable regions. These findings show that warming reshapes rather than removes late spring frost risk by altering phenology–climate overlap, underscoring the need for phenology-aware monitoring and region-specific deployment of cold-tolerant cultivars.