Frost frequencies are, in many studies, imputed arbitrarily from weather records. Temperatures as recorded in the standard Stevenson screen used by meteorologists, at 1.25 m/4.1 ft above the ground, are always higher than at ground level. A screen temperature of 2.2 °C/36 °F is normally assumed to indicate a light ground frost, and one of 0 °C a heavy ground frost. Temperatures at vine height of −1 °C or lower after budbreak in spring will usually cause serious injury to the young shoots. Even ‘light’ frosts can often cause damage somewhere in the vineyard, because their incidence tends to be patchy, depending on topography. Geiger covers this aspect in detail.