tåge

Tåge, or fog, is a weather phenomenon in which a large concentration of tiny water droplets is suspended close to the ground, reducing visibility to commonly less than 1 kilometer (0.6 miles). Fog is a type of low-lying cloud that forms at or near the surface and can vary in thickness. When visibility improves, the fog dissipates.

Fog forms when moist air near the surface cools to or below its dew point, causing water vapor to condense into droplets. It can also develop when warm, moist air moves over a cooler surface, or when air at different temperatures and humidity levels mixes. Common forms include radiation fog, which forms on clear, calm nights as the ground loses heat; advection fog, created when warm, moist air moves over a cooler surface; upslope fog, which occurs as air is lifted up terrain and cools; and evaporation fog, produced when cold air passes over warm water, adding moisture to the air.

Fog is most frequent in regions with high humidity and light winds, such as coastal areas and valleys, and it often appears in autumn and winter in temperate climates. It can last from minutes to several hours, and the duration depends on wind, temperature changes, and sunlight.

Impacts include travel disruption and safety hazards for road, rail, and air transport. Forecasting relies on meteorological observations of temperature, humidity, and dew point, along with wind and cloud cover, to predict fog formation and dissipation. In daily life, drivers are advised to reduce speed, use low beam headlights, and maintain a greater following distance when fog reduces visibility.