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Dew point

Dew point, also known as dew point temperature, is the temperature to which the air has to cool down in order for water vapour to condense. Dew point provides information on humidity.


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Dew point temperature is given in degrees Celsius (°C). This value is measured at the automatic weather stations in the MeteoSwiss monitoring network. When humidity remains constant and the air has cooled down to dew point temperature, this means the air is saturated with water vapour. This condenses and either settles on the ground as dew, or it forms fog or low stratus cloud

Muggy air

When the dew point is close to the air temperature, this means the relative humidity is high. Conversely, a dew point well below the air temperature indicates that relative humidity is low and the air is dry. In summer, when the air is warm and humid, the dew point temperature can be as high as around 20°C in Switzerland. The air is then sometimes described as muggy, such as during thunderstorms.

Very dry air

At low elevations in winter, when the air is cold and dry, the dew point can be less than -10°C. In winter in the mountains, the dew point can sometimes drop below -20 to -30°C during high-pressure conditions, even when the air temperature is above zero. At the Jungfraujoch station (3,571 m), the dew point has been as low as ‑50°C (at an air temperature of -13°C). This corresponds to a relative humidity of around 5 percent.