Black frost is a type of frost especially damaging to agriculture that occurs when temperature drops below 0 °C under conditions of very dry air (low relative humidity). Unlike white frost (visible hoarfrost), no ice deposit forms on surfaces because the dew point is well below 0 °C and there is insufficient water vapour to condense and freeze. The name "black" comes from the dark, withered appearance of damaged plant tissues. The destructive mechanism is insidious: water inside plant cells freezes, ice crystals rupture cell membranes, and upon thawing the tissue collapses and darkens. Black frost is more destructive than white frost because the hoarfrost of white frost paradoxically acts as thermal insulation, partially protecting tissues; additionally, sublimation of hoarfrost releases some latent heat. Without this protection, black frost freezes tissues more deeply. In agricultural regions, black frost is feared especially during fruit tree flowering (February–April): damage can destroy entire harvests of almonds, cherries, peaches, and vineyards. Conditions favouring it include clear nights, calm winds, winter anticyclones, and dry continental air masses. Farmers employ protection methods such as fans, heaters, and micro-sprinklers, though against black frost early detection remains the best defence.