Frost days per year - (ECMWF)

Number of frost days (temp < 0° C) per year for the timeframe 2000 - 2020.

As suggested by FAO, when air temperatures fall below 0 degree celsius, sensitive crops can be injured, with significant effects on production. Water within plants may or may not freeze during a frost event, depending on several avoidance factors. A "freeze" occurs when extracellular water within the plant freezes (i.e. changes from liquid to ice). This may or may not lead to damage of the plant tissue, depending on tolerance factors (e.g. solute content of the cells). A frost event becomes a freeze event when extracellular ice forms inside of the plants. Freeze injury occurs when the plant tissue temperature falls below a critical value where there is an irreversible physiological condition that is conducive to death or malfunction of the plant cells

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