Drought and Extreme Heat Reduce Wheat and Maize Production in the United States by Lowering Both Crop Yields and Harvestable Fraction

Abstract Ensuring food security is crucial in the context of climate change and increased extreme weather events. Crop production depends not only on yield but also on the harvestable fraction (HF), the ratio of harvested areas to planted areas. While the impacts of climate fluctuations on crop yields are well‐document, the role of HF‐a critical yet underexplored factor‐remains poorly understood. This study introduces HF as a key metric for assessing how temperature, drought, and precipitation affect the production of major staple crops (winter wheat, spring wheat, and maize) in the United States at the county level. Our findings indicate that Killing Degree Days (KDD) and Drought Days (DD) are key drivers of production declines, reducing both yield and HF. From 1982 to 2020, changes in KDD and DD led to more significant reductions in crop production in the Midwest compared to other regions. Projections for 2021–2100 under different Shared Socioeconomic Pathways (SSPs) indicate even steeper declines in yield, HF and production, especially under the high‐emission scenario (SSP5‐8.5), with anticipated net production decreases of 6.08%, 8.2%, and 7.57% for the three crops. Although HF may increase in colder regions, this does not offset losses in warmer areas, leading to net HF decreases of 0.36%, 2.09%, and 5.82% for the three crops. This study finds that drought and extreme heat considerably reduce food production by simultaneously lowering yields and HF and underscores the need for adaptive strategies that address both yield and HF to enhance food security in a changing climate.