Abstract: Silage maize (Zea mays) has become a crucial dual-purpose grain–forage crop in Chinese agriculture. As one of the most widely used forage crops, its cultivation potential is significantly affected by effective accumulated temperature. Although many studies have been conducted to improve the yield and nutritional quality of silage maize, research on appropriate planting systems for double-crop silage maize in different regions remains relatively limited. To rationally plan planting regimes for double-crop silage maize under the diverse climatic conditions of Hebei Province, this study conducted a field experiment in 2024 at the Nanpi Ecological Agriculture Experimental Station, Chinese Academy of Sciences (38.04°N, 116.40°E) in Cangzhou City — a typical semiarid agricultural ecosystem in the North China Plain. The experimental materials included ten maize varieties suitable for both grain and forage use, with growth periods that meet the requirements for two cropping cycles per year: ‘Beinong 368’ ‘Boke 1066’ ‘Dongdan 1775’ ‘Ganyu 331’ ‘Huayu 698’ ‘Jinling 327’ ‘Jiyuan 888’ ‘Liangyu 99’ ‘Weike 966’, and ‘Zhengdan 958’. Throughout the growing season, the phenological stages of each variety were recorded — including emergence, jointing, silking, blister, milk, and early dough stages — and the effective accumulated temperature (the sum of daily average temperatures above 10 ℃ during the growth period) was calculated for each variety in both growing seasons. Based on the average effective accumulated temperature (A) across the two seasons, the tested varieties were divided into three maturity groups: early maturing (A < 1 200 ℃·d), medium maturing (1 200 ≤ A < 1 250 ℃·d), and late maturing (A ≥ 1 250 ℃·d), resulting in six possible double-crop combinations: early-early, early-medium, early-late, medium-medium, medium-late, and late-late maturing. To scale these experimental findings spatiotemporally, the study integrated meteorological data from 123 county-level stations in Hebei Province over 45 years (1976–2020). A strict data quality control protocol was implemented, and the Inverse Distance Weighting (IDW) interpolation method was used to estimate missing values, ensuring complete spatial coverage and maintaining the integrity of thermal regime analysis. Results showed that the overall interannual variation rate of effective accumulated temperature ≥ 0 ℃ in Hebei Province was 7.37 ℃·d·a⁻¹, indicating a steadily increasing trend. Areas with relatively low effective accumulated temperature (≤ 1 100 ℃·d) were concentrated in Zhangjiakou and Chengde from 1976 to 2020, with only minor changes in range. Conversely, areas with higher values (≥ 2 200 ℃·d) expanded significantly. By 2020, areas suitable for double-cropping silage maize had shifted northward in response to climate warming, and viable planting zones were identified for all six maturity combinations. This study demonstrates that climate warming has significantly influenced the planting potential of double-crop silage maize in Hebei Province. In conclusion, continued global climate warming is likely to increase effective accumulated temperature further, thereby enhancing heat resource availability and expanding the feasible areas for various maturity combinations. The methodological framework established here — integrating precise field experimentation with comprehensive climate analysis — offers a model for evaluating planting system adaptation to climate change in other temperate regions. Future research should incorporate additional environmental and economic variables to develop robust decision-support tools for farmers and policymakers facing climate-induced agricultural transitions.