Weather Glossary
Dictionary of meteorological terms to better understand forecasts
Anticyclone
An area of high atmospheric pressure characterized by generally stable and clear weather. Air descends and warms up, preventing cloud formation.
AQI (Air Quality Index)
An index that measures the concentration of atmospheric pollutants. Ranges from 1 (good) to 5 (very poor) and indicates the potential impact on health.
Atmosphere
The layer of gases surrounding the Earth, composed mainly of nitrogen (78%) and oxygen (21%). All meteorological phenomena occur within the atmosphere.
Breeze
A light to moderate wind. Sea breezes blow from sea to land during the day; land breezes blow from land to sea at night.
Drizzle
Precipitation consisting of very fine water droplets (less than 0.5 mm in diameter) falling slowly and uniformly.
Celsius (°C)
Unit of temperature measurement. The Celsius scale sets the freezing point of water at 0°C and its boiling point at 100°C at sea level.
Clear sky
A meteorological condition where cloud cover is less than 10%. Also called "cloudless sky".
Cumulus
White, fluffy clouds with a flat base and rounded top, typical of fair weather. They can develop into stormy cumulonimbus clouds.
Depression (Low)
An area of low atmospheric pressure associated with generally unstable weather including clouds and precipitation. Air rises, cools and forms clouds.
Degrees
Unit of measurement for temperature (°C, °F) or for angles (wind direction in degrees: 0° = North, 90° = East, 180° = South, 270° = West).
Evaporation
The transformation of liquid water into water vapor through heat. It is a key process in the water cycle.
Front
A transition zone between two air masses of different temperatures. A cold front brings colder air; a warm front brings milder air.
Cold front
A boundary where cold air replaces warm air. Often causes intense but brief precipitation and a drop in temperature.
Fog
A cloud at ground level reducing visibility to less than 1 km. Forms when humid air cools and water vapor condenses into tiny droplets.
Hail
Solid precipitation in the form of ice pellets larger than 5 mm in diameter. Forms in cumulonimbus clouds during severe thunderstorms.
hPa (Hectopascal)
Unit of atmospheric pressure measurement. 1 hPa = 100 Pascals. Normal pressure at sea level is approximately 1013 hPa.
Relative humidity
The percentage of water vapor present in the air relative to the maximum amount the air can hold at that temperature. Ranges from 0% (very dry) to 100% (saturated).
Isobar
A line on a weather map connecting points of equal atmospheric pressure. Used to visualize high and low pressure areas.
Meteorology
The science that studies atmospheric phenomena to understand and predict the weather.
mm (Millimetre)
Unit of precipitation measurement. 1 mm of rain equals 1 litre of water per square metre.
Precipitation
Water falling from the atmosphere to the ground in liquid form (rain, drizzle) or solid form (snow, hail, sleet).
Atmospheric pressure
The force exerted by the weight of air on a surface. Measured in hPa, it greatly influences the weather.
Weather forecast
An estimate of future weather conditions based on complex mathematical models and analysis of millions of data points.
Gust
A sudden, brief increase in wind speed. Gusts can be significantly stronger than the average wind.
Solar radiation
Energy emitted by the Sun as light and heat. The main driver of meteorology and Earth's climate.
Snow
Solid precipitation formed by ice crystals. Occurs when temperatures remain below 0°C throughout the air layer.
Storm
A violent atmospheric disturbance characterized by very strong winds (over 90 km/h) often accompanied by heavy rain.
Temperature
A measure of the degree of heat or cold in the air. Varies with time of day, season, latitude and altitude.
Feels like (apparent temperature)
The temperature perceived by the human body taking into account wind and humidity. Can differ significantly from the actual temperature.
Thunderstorm
A violent weather phenomenon characterized by lightning, thunder, heavy rain and sometimes hail. Forms in cumulonimbus clouds.
Wind
The horizontal movement of air caused by differences in atmospheric pressure. Always flows from high pressure to low pressure areas.
Visibility
The maximum distance at which an object can be clearly distinguished. Can be reduced by fog, rain, snow or pollution.
> This glossary is regularly updated with new terms. If you would like the definition of a specific term, feel free to contact us.