50 Fun Facts About Thunderstorms

Thunderstorms occur in which type of cloud?

Cumulonimbus clouds tower high enough for ice crystals and soft hail to collide inside them, and those countless collisions build up the electric charge that lightning releases.

What is the first phase of a thunderstorm's life cycle called?

The cumulus stage begins when heated ground, colliding winds or rising terrain push moist air upward; as its vapour condenses it gives off heat, which keeps the young cloud climbing.

What gives a mature thunderstorm cloud its characteristic anvil shape?

Air spreading out at the tropopause flattens the cloud top: the stable, warmer layer above works like a lid the rising air cannot punch through, so it fans out sideways instead.

What marks the mature stage of a thunderstorm?

Both an updraft and a downdraft at once: falling rain drags air down beside the rising current, which is why this is the stage of hail, the heaviest rain and the most frequent lightning.

Forecasters' slang for scattered summer-afternoon thunderstorms is named after which snack?

Popcorn convection: the storms burst up here and there in the afternoon heat, and each dies within about an hour as its own rain-cooled downdraft chokes the updraft that feeds it.

What atmospheric ingredient allows a storm to become a long-lived supercell?

Vertical wind shear tilts the storm so that its rain falls beside the updraft instead of straight back through it, letting the storm feed itself for hours rather than minutes.

What is the rotating updraft inside a supercell called?

A mesocyclone shows up on Doppler radar as winds racing toward and away from the dish side by side, which lets forecasters warn of a possible tornado before one has formed.

Which radar signature, traced by rain wrapping around a supercell's rotation, warns that a tornado may form?

A hook echo forms as the storm's rear downdraft drags rain and hail around the back of the updraft; an Illinois engineer working on a radar first caught one beside a confirmed tornado in 1953.

Which is the most common type of thunderstorm development?

Multi-cell clusters renew themselves: each cell's cold outflow joins a shared gust front that lifts warm air into a fresh cell every few minutes, so the cluster outlives any single cell by hours.

A squall line that bulges outward on radar is called what?

A bow echo bends because a jet of air rushing in behind the line pushes its middle ahead of the ends, so the most damaging straight-line winds strike near the crest of the bulge.

Which fast-moving windstorms, born from lines of summer thunderstorms, flatten trees across hundreds of miles with straight-line gusts?

Derechos take their name from the Spanish for 'straight': an Iowa physics professor coined it in 1888 to set their straight-line winds against the turning winds of a tornado.

In the US, hail as wide as which coin makes a thunderstorm officially 'severe'?

A quarter, about an inch wide: until 2010 the bar was penny-sized hail, but it was raised after studies found smaller stones did little damage and people were tuning out the frequent warnings.

Mesoscale convective systems, vast thunderstorm complexes, supply much of the summer rain for which US region?

The Great Plains get these complexes when afternoon storms merge into one system that can last more than twelve hours, raining on through the night and often into the next morning.

Severe thunderclouds sometimes take on which eerie tint, long linked in folklore to hail?

Green: one leading idea is that clouds heavy with water scatter bluish light, which the red glow of a low sun turns green, though studies have found no proof that the tint means hail or a tornado.

Medieval Europeans tried to drive hailstorms away from their crops by firing cannons and sounding what?

Church bells later gave way to purpose-built 'hail cannons', which some growers still fire at approaching storms, though a 2006 scientific review called them a waste of money and effort.

The largest hailstone recovered in the United States, found in South Dakota in 2010, was about as wide as which ball?

A volleyball: the stone measured 8 inches across and weighed nearly two pounds, and it had already shrunk, because a power cut hit the finder's home before weather officials could measure it.

Which of these does the US National Weather Service call safe to use indoors during a thunderstorm?

A cordless phone has no wire to bring a strike's current to your hand; lightning that hits a building can run through its wiring and plumbing, so corded phones, computers and taps are out.

What name is given to an intense fear of thunder and lightning?

Astraphobia comes from the Greek for lightning; many children have the fear and grow out of it, while sufferers of any age may watch the weather anxiously for any sign of a coming storm.

What is the strongest category on the Enhanced Fujita tornado scale?

An EF5 is judged from the wreckage, not from measured wind: surveyors rate a tornado by what it destroyed, and the top category typically means well-built houses swept clean off their foundations.

NOAA's tornado probe TOTO inspired the sensor barrel Dorothy in which disaster film?

Twister borrowed the idea from the Totable Tornado Observatory, a drum of sensors that government scientists spent years trying to set down in a tornado's path, with little success; it was named after Dorothy's dog in The Wizard of Oz.

What is a waterspout, technically?

A tornado over water, though the commonest kind is the weak 'fair-weather' spout, which starts at the water's surface and climbs upward instead of dropping from a rotating storm.

What is sinking air that slams into the ground beneath a thunderstorm called?

A downburst can suddenly rob a landing aircraft of lift; several fatal airliner crashes were blamed on them, which is why pilots now train to recognise and escape one.

What triggers the medical phenomenon known as 'thunderstorm asthma'?

Pollen grains bursting into tiny fragments slip past the nose and deep into the lungs; one 2016 storm over Melbourne left thousands struggling to breathe within hours and overwhelmed the city's ambulances.

Roughly how many thunderstorms are occurring on Earth at any given moment?

About 2,000 at once adds up to some 16 million thunderstorms a year, most of them over tropical land, where the daily build-up of heat and moisture sets them off almost every afternoon.

A thunderstorm nicknamed Hector forms over the Tiwi Islands almost every wet-season afternoon, within sight of which Australian city?

Darwin: Hector builds in the same spot so reliably, as sea breezes collide over the islands, that Second World War pilots steered by the towering cloud and gave it its name.

In summer, air-mass thunderstorms are an almost daily occurrence in which US state?

Florida is a peninsula with warm water on both sides: on summer afternoons the sea breezes from the Gulf and the Atlantic push inland, collide over the land and force the humid air upward.

The energy a typical thunderstorm releases is often likened to that of which weapon?

The Hiroshima atomic bomb released less energy than an ordinary storm does, but the storm lets it out slowly: nearly all of it is heat given off as water vapour condenses into cloud.

In 2011, NASA announced that its Fermi space telescope had caught thunderstorms hurling beams of what into space?

Antimatter: gamma-ray flashes tied to lightning create electrons and positrons, and in one case the particles rode the Earth's magnetic field from a storm over Zambia to strike Fermi above Egypt.

Which field research project used 'Doppler on Wheels' radar trucks to study tornadic storms?

Storm chasers head to the Great Plains and Canadian Prairies every spring.

In Norse myth, the thunder god Thor rode a chariot pulled by which animals?

Goats: in the Prose Edda Thor cooks and eats his pair for supper and raises them to life with his hammer next morning, but a farmer's son has cracked a leg bone for the marrow, and one goat comes back lame.

Which Hindu god is recognised as the god of rain and thunderstorms?

Indra wields the thunderbolt called the vajra, and in the Rigveda he uses it to kill the serpent Vritra, who had been holding back the rivers, so that the waters can flow again.

Which religious reformer vowed to become a monk after being caught in a thunderstorm?

Martin Luther, then a law student, cried 'Help! Saint Anna, I will become a monk!' as a bolt struck near him in 1505; he entered a monastery within weeks, to his father's fury.

Storms on which planet can throw lightning far more powerful than Earth's?

Jupiter's storms are driven by heat rising from the planet's interior, not by sunlight, yet they are thought to work much as ours do: moist air rises, its water condenses, and charge builds until it flashes.

To roughly what temperature does the air around a lightning flash heat?

About 30,000 °C, roughly five times hotter than the surface of the Sun: the air is heated so fast that it expands explosively, and that shock wave is the thunder.

Most lightning flashes never touch the ground, so where does the typical flash stay?

Within a single cloud: the charge usually leaps between the cloud's own oppositely charged layers, which is why a distant storm can flicker from inside without sending a single bolt to earth.

What tubular structures form when lightning melts sandy soil?

Fulgurites, named from the Latin for lightning, are natural glass: the bolt melts the sand in an instant, and the hollow tube left behind traces the path the current took through the ground.

Counting seconds between flash and thunder, roughly how many seconds equal one kilometre of distance?

Three seconds per kilometre, or five per mile, because sound covers about 340 metres a second while the flash arrives at once; if you can hear the thunder at all, you are close enough to be struck.

Which New York skyscraper does lightning strike about 23 times a year?

The Empire State Building shows why the old saying is wrong: lightning favours tall, pointed, isolated objects, so far from never striking twice, it hits the same spire again and again.

Over which Venezuelan body of water does the 'everlasting storm' of Catatumbo lightning occur?

Lake Maracaibo's storm returns on so many nights, and can be seen from so far away, that sailors steered by it for centuries and called it the 'Lighthouse of Maracaibo'.

Park ranger Roy Sullivan survived a record how many lightning strikes between 1942 and 1977?

Seven strikes, by Guinness's count: the fourth set his hair alight, and after that he kept a can of water in his truck, which he needed when the next bolt did the same.

Red sprites are electrical discharges that occur where?

High above thunderclouds in the mesosphere, sprites were glimpsed by pilots for many years before Minnesota scientists testing a low-light camera in 1989 recorded one by accident.

Which 18th-century experimenter invented the lightning rod after proposing that lightning was electricity?

Benjamin Franklin never patented the rod, wanting it freely copied; in 1754 the Czech priest Prokop Diviš raised a well-grounded 'weather machine' that some count as a separate invention.

Which lightning god belongs to Aztec mythology?

Tlaloc was feared as well as thanked: the Aztec rain god sent the showers the maize needed, but also hail, thunder and lightning, and children were sacrificed to him at mountain shrines.

Which name is given to silent flashes on the horizon on summer nights, really just lightning too distant to hear?

Heat lightning is a misnomer: warmth has nothing to do with it, and the flashes come from an ordinary storm so far off, often below the horizon, that its thunder fades out before reaching you.

A squall line of thunderstorms most often forms along or just ahead of which weather feature?

A cold front wedges under the warm, moist air ahead of it and heaves it upward along its whole length, so the storms it sets off line up in a band that can run for hundreds of miles.

A 'training' thunderstorm, where new cells keep forming upwind, caused a deadly 1972 flash flood where in South Dakota?

Rapid City suffered most of the flood's 238 deaths because homes had been built along Rapid Creek; afterwards the city cleared the flood plain and turned most of it into parks.

Why is hail more common along mountain ranges?

Orographic lifting strengthens updrafts because mountains shove the wind upward, and the stronger the updraft, the longer a hailstone stays aloft gathering ice before it grows too heavy and falls.

A lightning bolt makes the air's two main gases combine, adding which acid to rain?

Nitric acid from lightning feeds the land: once rain carries it into the soil it becomes nitrate, a natural fertiliser, and one of the few routes by which the air's nitrogen reaches plants.

A 9th-century hailstorm is thought to have killed hundreds of pilgrims at Roopkund, the Himalayan 'Skeleton Lake' in which country?

India: the lake lies about 5,000 metres up in Uttarakhand, and many of its older skulls carry round dents from above, though a 2019 DNA study found that other victims died there a thousand years later.

Which three US states meet in the region nicknamed 'Hail Alley'?

Colorado, Nebraska and Wyoming meet on high plains in the lee of the Rockies, where the freezing level is so low that hailstones reach the ground before they have time to melt.