a to z
Weather glossary explained.
What does dew point, jet stream or wind chill actually mean? Every weather term used in a forecast, explained clearly and linked to related terms and full articles.
Air Quality Index (AQI)
A standardised scale, usually 0 to 500, that reports how polluted the air is and what health precautions, if any, are advisable.
Read more →Barometric Pressure
The weight of the atmosphere pressing down at a given location, measured in units such as hectopascals or inches of mercury.
Read more →Cold Front
The leading edge of an advancing mass of cooler air, which typically brings a sharp, short burst of rain or storms as it passes.
Read more →Dew Point
The temperature at which air becomes saturated with moisture and water vapour starts to condense into dew, fog or clouds.
Read more →El Niño and La Niña
Opposite phases of a recurring Pacific Ocean pattern that shifts global weather by changing sea-surface temperatures near the equator.
Read more →Fog
A cloud that forms at ground level, reducing visibility to less than roughly one kilometre.
Read more →Frost
A thin layer of ice crystals that forms on surfaces when the air temperature at ground level drops to 0°C or below.
Read more →Heat Index
A single number that combines air temperature and humidity to estimate how hot it actually feels to the human body.
Read more →High-Pressure System
An area where atmospheric pressure is higher than its surroundings, usually bringing settled, drier weather.
Read more →Isobar
A line on a weather map connecting points of equal atmospheric pressure, used to visualise high- and low-pressure systems.
Read more →Jet Stream
A narrow band of fast-moving air high in the atmosphere that steers weather systems across the mid-latitudes.
Read more →Low-Pressure System
An area where atmospheric pressure is lower than its surroundings, typically associated with clouds, rain and unsettled weather.
Read more →Monsoon
A seasonal reversal of wind direction that brings a distinct wet season to large parts of Asia, West Africa and northern Australia.
Read more →Occluded Front
A weather front formed when a faster-moving cold front catches up with a slower warm front, lifting the warm air between them off the ground.
Read more →Polar Vortex
A large, persistent area of low pressure and cold air that circles each of Earth's poles, strongest in winter.
Read more →Precipitation
Any form of water, liquid or frozen, that falls from clouds to the ground, including rain, snow, sleet and hail.
Read more →Relative Humidity
The amount of moisture in the air expressed as a percentage of the maximum the air could hold at that temperature.
Read more →Thunderstorm
A storm producing lightning and thunder, usually formed by rapidly rising warm, moist air building into a towering cumulonimbus cloud.
Read more →UV Index
A scale, typically 0 to 11+, describing the strength of ultraviolet radiation from the sun and the sunburn risk it poses.
Read more →Visibility
The greatest distance at which an object can still be clearly seen against the sky, used to describe how fog, rain, snow or haze affect sight.
Read more →Warm Front
The leading edge of an advancing mass of warmer air, which typically brings a longer period of lighter, steadier rain than a cold front.
Read more →Wind Chill
A measure of how much colder moving air makes a given temperature feel, by speeding up the rate the body loses heat.
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