Atmosphere and weather

A convective storm cell with lightning and thunder that can bring heavy rain, gusts and hail.

Also: storm cell, severe storm

An electrical discharge between cloud and ground that ignites fires, injures people and damages electronics and power lines.

Also: electrical storm

A concentrated downdraught that spreads out at the ground as a short burst of damaging straight-line wind.

Also: microburst, straight-line wind

A violently rotating column of air in contact with the ground, leaving a narrow and intense damage path.

Also: twister

A tornado-like rotating column over open water that endangers boats, ports and shorelines.

Falling ice stones large enough to ruin crops and to break glass, roofs, vehicles and solar panels.

Also: hailstorm

A sudden, short surge of wind, often along a line of storms, with a rapid shift in direction and a burst of rain.

Also: squall line, gust front

A long-lived storm system whose gust front causes widespread straight-line wind damage along a path hundreds of kilometres long.

A thunderstorm grown from the heat of a large fire that throws embers far ahead, makes erratic winds and dry lightning, and lofts smoke into the stratosphere.

Also: pyrocumulonimbus, pyroCb, firestorm cloud

Thunderstorms whose rain evaporates before reaching the ground, so lightning strikes dry fuel and ignites many fires at once across a wide area.

Also: dry thunderstorm

A sudden wave of severe asthma attacks when storm outflow ruptures pollen grains into fine fragments that people breathe deep into their lungs.

Also: epidemic thunderstorm asthma, Thunderstorm asthma event

A warm-core rotating storm over tropical oceans whose winds, rain and surge threaten coasts and inland river basins.

Also: hurricane, typhoon, cyclone

A hybrid storm with both tropical and mid-latitude traits and a wide wind field, often weaker at its core.

A frontal low-pressure storm of the middle latitudes that brings wind, rain or snow over a wide area.

Also: frontal low, winter storm system

A closed circulation of low surface pressure that organises cloud, rain and wind; the general storm driver when no more specific storm type applies.

Also: depression

A compact, warm-cored cyclone over the Mediterranean with tropical-storm structure that brings violent wind, torrential rain and surge to coasts with little preparation.

Also: medicane

A small, intense maritime cyclone forming in cold air over polar seas that brings sudden gales, heavy snow and icing to shipping and coastal settlements.

Also: arctic hurricane

A tropical cyclone strengthening very quickly, often over warm water near landfall, leaving too little time for warnings and evacuations to match the storm.

Also: rapid intensification, explosive tropical strengthening

Very rapid deepening of a mid-latitude low that produces hurricane-force wind, heavy snow or rain and coastal surge within a day.

Also: bomb cyclone, weather bomb

Damaging non-convective wind from a steep pressure gradient, bringing treefall, structural damage and power-line failure.

Also: strong wind, high wind

Sustained strong wind that disrupts shipping, aviation and construction and can damage exposed structures.

Also: storm-force wind

A warm or cold, dry and gusty wind descending a mountain lee slope that fans fires and damages structures.

Also: foehn, chinook, katabatic wind

Invisible turbulent air, usually near the jet stream, that injures aircraft occupants and strains airframes.

Also: aviation turbulence

Rain falling fast or long enough to overwhelm drainage, soils and streams and to trigger floods and slope failures.

Also: extreme rain, cloudburst, torrential rain

Snow accumulating fast enough to halt transport, load roofs and lines, and strand people.

Also: snow

Heavy snow with moderate to strong wind that cuts visibility and mobility across a wide area for a day or more.

Strong wind lifting or driving snow so that visibility collapses, with extreme cold and rapid drifting.

Also: whiteout

Narrow, intense snow bands formed when cold air crosses warmer open water and drops its moisture downwind.

Rain that freezes on contact and coats surfaces with ice, breaking trees and lines and making roads impassable.

Also: ice storm, glaze

Ice building up on aircraft, vessels, lines and towers until the added load or lost performance causes failure.

Also: ice accretion, aircraft icing, vessel icing

A spell of abnormally high temperature, often with warm nights, that overloads bodies, power grids and crops.

Also: extreme heat, heat spell

Heat combined with high humidity so that sweating can no longer cool the body, even at moderate air temperature.

Also: wet-bulb extreme

A spell of abnormally low temperature that strains heating, freezes pipes and endangers exposed people and livestock.

Also: extreme cold, cold snap, wind chill

A harsh winter of deep snow, ice crust or extreme cold that blocks grazing and kills herds on open range.

Also: dzud

Air temperature falling well below freezing for hours, killing crops, bursting pipes and stopping water flow.

Also: freeze

Ice deposits on surfaces and plants when temperature drops to freezing, including ground frost that damages seedlings and blossoms.

Also: ground frost, hoar frost

A sudden warm spell that melts snow and ground ice faster than the ground can absorb, loosening slopes and swelling rivers.

Also: sudden thaw

Nights that stay hot enough to prevent the body recovering from daytime heat, raising deaths among older and sick people and in poorly ventilated homes.

Also: tropical nights, warm nights

Persistent extra heat in built-up areas from sealed surfaces, waste heat and lack of shade, which deepens heatwaves and night-time heat for city dwellers.

Also: urban overheating, city heat excess, Urban heat island stress, city heat retention, heat island.

Water droplets near the ground cutting visibility to the point that aircraft, vessels and road traffic stop or crash.

Also: dense fog, low visibility

A wind-lifted wall of mineral dust that blinds traffic, fouls machinery and harms lungs.

Also: sandstorm, haboob

Fine mineral dust lingering in the air after a storm or from dry sources, thinning sunlight and sky clarity.

Also: sand haze

Fine suspended particles scattering light so that distant objects blur, from mixed dust, smoke or pollution.

Also: hazy sky

Combustion particles from fires carried downwind, degrading air and visibility far from the source.

Also: smoke, fire smoke

A season or episode of very high pollen or spore counts, lengthened by warming and rising carbon dioxide, that triggers allergic disease and asthma.

Also: high pollen season, pollen storm, aeroallergen

A long, narrow corridor of strong moisture transport that delivers extreme rain or snow where it meets a coast or mountains.

A persistent high-pressure pattern that parks weather systems and prolongs heat, cold, drought or rain over one area.

Also: blocking high

A multi-month warm or cool swing of the tropical Pacific that shifts rainfall, heat and storm tracks around the world.

Also: El Nino, La Nina, ENSO

A late, weak or broken seasonal rain system that leaves a rain-fed region short of water in its main growing season.

Also: weak monsoon, late monsoon

A breakdown or displacement of the stratospheric polar vortex that can send waves of Arctic air to the middle latitudes weeks later.

Also: sudden stratospheric warming

A swing in the temperature contrast across the tropical Indian Ocean that brings drought and fire to one side of the basin and floods to the other.

Also: positive dipole, negative dipole

A strong, persistent phase of the pressure seesaw over the North Atlantic that steers winter storms, rain and cold spells across Europe and eastern North America.

Also: North Atlantic Oscillation, NAO extreme

Very high ground-level ultraviolet radiation that burns skin and eyes and harms crops and plankton.

Also: high UV index

A seasonal or sustained thinning of the ozone layer that lets more ultraviolet radiation reach the surface.

Also: ozone hole