Kids ask a lot of questions. Usually, we know the answers. But every now and then, you’ll be given a bit of a curve ball. Did you ever stop to think where the wind comes from or how wet a cloud would feel? Read on for straightforward answers to tricky weather questions.
What Makes The Wind Blow?
Putting aside ‘dad jokes’ about baked beans, it can be difficult to explain where wind comes from. The answer hinges on atmospheric pressure, which is an aspect of the weather we can’t easily see or feel. But here’s one way to look at it.
The air above us has weight. This is easy to understand. When you wave your hand about, you can feel the air. You’re pushing it. The air is a thing.
Wind is similarly caused when air moves. But there’s no god-like hand doing the pushing. Rather, it’s a block of air at high pressure moving to fill an area of lower pressure. Gases always do this. Think of the pressurised steam that shoots out of your kettle into the less pressurised air of your kitchen. It never happens the other way round.
Why does the air find itself at different pressures in the first place? This is caused by many factors, but the main one is the Sun. During the daytime, the Sun heats up the ground. This heat is passed on to the air -- you can feel this by placing your hand a centimetre above a patio stone on a hot day. But the effect is uneven. The sun’s rays hit different parts of the Earth at different angles. Fields pass on heat differently to oceans or mountains or concrete. We get a patchwork of different temperatures.
As everyone knows, hot air rises (it’s how a hot-air balloon works). As the warmed air rises, it leaves behind a pocket of low pressure. Surrounding air, which hasn’t been warmed to the same degree, rushes in to equalise the pressure. This we feel as wind.
One of the easiest places to get a feel for all this is at the seaside. We’ve all felt the cooling sea breeze blowing in from the ocean. Land heats up more quickly than sea. This means more hot air rises over the coast than over the waves. This creates the pressure difference. Air from the sea rushes in to fill the lower-pressure zone over the coast. (A reverse effect can happen at night, when the land cools quicker than the sea.)
The picture is more complicated than this, and we haven’t even mentioned weather fronts. But if you just imagine hot air rising, and neighbouring air breezing in to fill the vacancy, then you have an elementary idea of the wind.
What’s The Difference Between Hail And Sleet?
We’ve all heard the patter of small ice pellets against the windows, but was it hail or sleet? What’s the difference? In simple terms, hail comes from thunderstorms (usually in the summer), while sleet comes from regular rain clouds on very cold days (usually in the winter).
Hail is formed when newly precipitated raindrops are lifted by an updraft, high into the clouds. Here they form ice crystals, usually around dust particles. This creates a hard pellet, which plummets back down. It may get lifted several more times to form an ever-growing pellet. Once the hailstone is too heavy to remain aloft, it falls to the ground with a thump. Hail varies in size, but even the smallest pellets will make a din on a roof or window. The largest hailstones can reach 6cm in diameter and can cause damage or injury.
Sleet, on the other hand, is a much gentler thing. It forms when snowflakes melt on their way down from the clouds, only to refreeze again when they hit a cool layer of air near the ground. Sleet pellets are usually smaller than hail, and are not associated with thunderstorms.
Can It Really Rain Cats And Dogs?
The phrase “raining cats and dogs” suggests a really heavy rainfall, which you wouldn’t want to go out in. No one knows where the saying comes from, but it’s been in use for at least 350 years and similar idioms can be found all over the world. It’s clearly meant as a figure of speech, but can animals really fall from the sky?
The answer appears to be ‘yes’. Countless examples of small animals falling like rain can be found across cultures and time periods. Small fish, frogs and other aquatic animals are the most commonly reported. How these creatures come to be up in the skies is still unproven. The most likely scenario would have them scooped out of a lake by a water spout, to be dropped several miles away when the swirling column weakens. Cats and dogs would probably be too heavy. Plus, they don’t tend to congregate in large groups, so would never be picked up and ‘precipitated’ en masse. Beware, by the way, of the videos and photos you’ll find online. Many are known to be fakes.
Would I Get Wet If I Walked Through A Cloud?
The short answer is “yes, but not very”. Passing through most clouds would be like walking through a fog. If the mist is dense enough, you might feel a little moisture on your skin, but you certainly won’t be soaked. Were you to freefall through a cloud (not recommended, and usually illegal) you’d feel a bit more moisture thanks to your speed. Passing through a rain cloud, where large droplets of water form and then fall, would be a different matter.
Does Lightning Really Never Strike The Same Place Twice?
This one’s a complete nonsense. Lightning can strike any part of the Earth’s surface, and does so an incredible 50 times every second. If, for some reason, it could never strike the same place twice, then it would have ran out of options many eons ago. Lighting has no memory. It can hit the same location over and over again. It’s easy to prove, too. Just google “Empire State Building lightning strike” and you’ll find dozens of examples of strikes hitting the same tower. Lightning can even hit the same person on more than one occasion. US park ranger Roy Sullivan has been dubbed both the unluckiest and the luckiest person in the world, having survived seven separate strikes.
Incidentally, you know that old trick about counting the seconds between lightning and thunder to work out the storm’s distance? It really works, at least as a rule of thumb. You have to remember, though, to divide by three. So if it takes 9 seconds for the thunder to reach your ears, then the strike was about 3 km away. (Divide by 5 for the distance in miles.) To learn more about lightning and electricity, see our explainer for KS2 kids.
Although originally from the Midlands, and trained as a biochemist, Matt has somehow found himself writing about London for a living. He's a former editor and long-time contributor to Londonist.com and has written several books about the capital. He's also the father of two preschoolers.