Heat-Stress days per year - (ECMWF) 

Number of heat-stress days (temp > 32° C) per year for the timeframe 2000 - 2020. 

This threshold is set as suggested by literature, i.e. in general terms temperatures above 32° C might affect plant growth. Based on the FAO Climate Smart Agriculture Sourcebook, extremely high temperatures above 30°C can do permanent physical damage to plants and, when they exceed 37°C, can even damage seeds during storage. The type of damage depends on the temperature, its persistence, and the rapidity of its increase or plants’ capacity to adjust. It also depends on the species and the stage of plant development. As the climate changes, the frequency of periods when temperatures rise above critical thresholds for maize, rice and wheat is predicted to increase worldwide. 

The data comes from ECMWF ERA5 Land hourly reanalysis dataset that is reduced to daily maximums.