aamukaste

Aamukaste, literally 'morning dew' in Estonian, is moisture that condenses on exposed surfaces during the early morning as air near the ground cools and reaches its dew point.

Formation and conditions: It forms when radiative cooling of surfaces at night lowers surface temperatures below the air's dew point, causing water vapor to condense. Clear skies, light winds, and high humidity promote dew, while dry, windy nights reduce it.

Where and when: Aamukaste is common in temperate climates and tends to be most apparent on grass, leaves, and other cool surfaces in spring and autumn.

Ecology and practical effects: Dew provides surface moisture that can aid plant hydration, especially for small plants. It can also create conditions favorable to fungal growth on leaves, and dew that lasts into the day may affect crops, vehicles, and mornings' visibility. It is generally unreliable as a sole water source for agriculture.

Notes: If temperatures fall below freezing, aamukaste droplets may freeze, forming frost.

See also: condensation, dew point.