nachtvorst

Nachtvorst, or night frost, is a meteorological phenomenon in which freezing temperatures occur during the night, leading to frost formation on surfaces. Frost is typically defined as surface or near-surface air temperatures at or below 0°C. Nachtvorst often arises from radiational cooling on clear, calm nights, when heat escapes from the ground into the sky and the air near the surface becomes very cold.

There are two main forms. Air frost refers to freezing temperatures in the air near the surface, while ground frost occurs when the surface or shallow soil freezes even if air temperatures are slightly above freezing. Hoarfrost can form when water vapor in the air deposits directly as ice crystals on exposed surfaces, especially under calm, dry conditions.

Frequency and seasonality vary by region. Nachtvorst is more common in temperate climates during late autumn, winter, and early spring, and is more likely inland or at higher elevations where radiational cooling is strong and humidity is low.

Impacts are most significant for agriculture and horticulture. Nachtvorst can damage buds, blossoms, and young leaves, reducing yields in fruit, vineyard, and vegetable crops. It can also affect ornamental plants and, in some cases, infrastructure and road surfaces due to frost-related processes.

Forecasting and mitigation are important. Meteorological services issue frost warnings, and farmers employ methods such as covering crops, irrigation to release latent heat, or using wind machines to mix warmer air. Selecting frost-tolerant varieties and adjusting planting times can further reduce risk.