Under the background of global warming, the frequent occurrence of extreme high temperature would threaten crop production greatly. Therefore, the spatial-temporal variations of high temperature during crop growth period based on several heat stress index were cleared, which was crucial for developing effective disaster risk management and adaptation measures.

In this study, the maize potential planting area was focused on. Based on the daily maximum temperature data from 1981 to 2060 in two Shared Socioeconomic Pathways scenarios (SSP1-2.6 and SSP5-8.5) of Coupled Model Intercomparison Project Phase 6 (CMIP6) and maize phenology data, we analyzed the spatial distribution and temporal trend of the heat stress intensity (HSI), accumulated heat stress days (AHSD), and heat degree-days (HDD) during flowering period of maize in the baseline period (1981-2014) and future period (2015-2060).

From 1981 to 2014, the HSI, AHSD and HDD during the flowering period of maize were the largest in Huang-Huai-Hai (HHH) and Northwest China (NWC), with the average value of 32.3 and 33.8 ℃, 8.4 and 9.8 d, 22.9 and 40.3 ℃·d, respectively. Due to climate warming, the high temperature during the flowering period of maize in China was characterized by long duration and wide range under the two climate scenarios, especially in SSP5-8.5. The largest temporal trend of HSI and AHSD occurred in Northern China (NC), under SSP1-2.6 and SSP5-8.5. The increasing trend of HSI were 0.97 and 1.16 ℃·(10a)^-1, and the increasing trend of AHSD were 0.73 and 1.11 d·(10a)^-1. The largest temporal trend of HDD occurred in HHH, under SSP1-2.6 and SSP5-8.5, with the increasing trend of 2.68 and 5.26 ℃·d·(10a)^-1.

In the future, the high temperature during the flowering period of maize in China was characterized by long duration and wide range, especially for HHH and NC. The former was mainly due to the high base temperature, and the latter was due to the large warming trend. The loss caused by high temperature could be reduced by selecting high temperature resistant varieties, adjusting the sowing window, adopting water, fertilizer, and chemical management measures.