Holidays in Belgium

Refers to how the outdoor air is expected to feel in degrees Celsius when actual temperature and relative humidity are combined (see humidex) or when actual temperature and wind are combined (see windchill).

Wind is the horizontal movement of air in relation to the earth's surface. Wind direction tells where the wind is blowing from. For example, a "north wind" is coming from the north and is blowing towards the south. There are four components of wind that are measured: direction, speed, character (i.e. whether it's a gust or a squall) and shifts.

A sudden significant increase in, or rapid variation of wind speed. Usually a gust lasts less than twenty seconds.

Relative humidity is a percentage of water vapour per area at a specific temperature. Relative humidity is calculated at all times of the year, but the humidex is usually only given in the warmer months from May to September.

Relative humidity can be calculated using various methods and instruments. It is a calculation to find out how many grams of water vapour can be held at a given temperature. Usually, the warmer the air, the higher its capacity for holding water vapour. Each specific temperature has a holding limit for water, and the actual amount of water held in the air at the time of measurement can be represented as a percentage. For example, if a parcel of air at 20ºC has a limit or capacity of 16 grams of water vapour and 16 grams of water vapour is measured, the air's holding capacity is at its maximum and the relative humidity (RH) of the air is said to be 100%. Take the same air with 8 grams of water vapour and your RH is 50%.

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