Crop-Season-Matched Climate Risks to Wheat and Maize Production in Henan Province, China: Evidence from a 29-Year Two-Way Fixed-Effects Panel

Aligning climate exposures with crop calendars is essential for credible climate-risk assessment in double-cropping systems. We quantified crop-season-matched precipitation and temperature effects on wheat and maize yields across 18 cities in Henan Province, China’s leading grain province, using a balanced panel of 522 city-year observations (1996–2024) and two-way fixed-effects models. Because winter wheat is harvested in early June and summer maize is sown in late June, wheat is modelled only against spring (March–May) climate and maize only against summer (June–August) climate. Spring precipitation significantly reduced wheat yield (elasticity −0.0299), and spring warming was associated with lower yield by 3.4% per °C once trends and province-wide shocks were removed; the apparent positive raw temperature correlation (+0.283) proved artefactual. Summer climate effects on maize were insignificant at the seasonal scale, consistent with irrigation buffering, but July heat and August rainfall revealed emerging vulnerabilities. Three documented extremes—2003 summer flood, July 2021 extreme rainfall, and 2023 harvest rain—were consistent with the panel mechanisms, with city-level yields falling 52–70%, up to 64%, and 11–16% below trend, respectively. K-means clustering identified three agro-climatic zones (robust to excluding yield variables), supporting spatially differentiated adaptation. Sensitivity analyses confirm that results hold when the wheat window is extended to March–June or when growing degree days replace mean temperature. Climate-risk assessment must be crop-, season-, and zone-specific.