Wind

Wind is simply air moving. It is caused by differences in air pressure, which themselves come from the Sun heating different parts of the Earth unevenly. Warm air rises (creating low pressure where it leaves) and cool air sinks (creating high pressure where it lands). Wind blows from high pressure to low pressure, just like water flows downhill. The bigger the pressure difference, the stronger the wind. Wind shapes the weather, drives ocean currents, scatters seeds, generates electricity in wind turbines, and has helped human civilisations cross oceans for thousands of years.

• Caused byPressure differencesDriven by uneven solar heating
• Speed measured byAnemometerOr estimated from effects (Beaufort scale)
• Strongest gust ever408 km/hBarrow Island, Australia, 1996
• Strongest sustainedApproximately 372 km/hMount Washington, USA, 1934
• Wind energy shareApproximately 9% of global electricityAnd growing fast
• Beaufort scale0 to 12Calm to hurricane

What causes wind

The basic cause of wind is the uneven heating of the Earth's surface by the Sun. The equator gets more direct sunlight than the poles. Land heats and cools faster than water. Mountains, deserts and forests all absorb heat differently. The result is constantly changing patterns of warm and cool air, creating regions of low and high pressure.

Wind blows from high pressure to low pressure, trying to even out the pressure differences. The bigger the difference, the stronger the wind. The Earth's rotation deflects the wind to one side (called the Coriolis effect), which is why storms in the Northern Hemisphere rotate anticlockwise and storms in the Southern Hemisphere rotate clockwise.

The Beaufort scale

The Beaufort scale was invented in 1805 by British Admiral Sir Francis Beaufort for ships to estimate wind speed from its observable effects. It runs from 0 to 12.

• 0 Calm: smoke rises straight up.
• 1 Light air: smoke drifts.
• 2 Light breeze: leaves rustle.
• 3 Gentle breeze: small branches move.
• 4 Moderate breeze: dust and loose paper raised.
• 5 Fresh breeze: small trees sway.
• 6 Strong breeze: large branches move, umbrellas hard to use.
• 7 Near gale: whole trees in motion, hard to walk against.
• 8 Gale: twigs break off trees.
• 9 Strong gale: roof tiles dislodged.
• 10 Storm: trees uprooted.
• 11 Violent storm: widespread damage.
• 12 Hurricane: devastating damage.

Global wind patterns

Earth's wind is organised into a few large-scale patterns called the global circulation.

• Trade winds: blow steadily from east to west in the tropics. Used by sailing ships to cross the Atlantic.
• Westerlies: blow from west to east in the middle latitudes, including over the UK and most of Europe. These bring most British weather.
• Polar easterlies: cold winds blowing from east to west near the poles.
• Jet streams: narrow ribbons of very fast wind (200+ km/h) high in the atmosphere. Airliners flying east try to catch them to save fuel.
• Monsoons: seasonal wind changes that bring heavy summer rain to South Asia, west Africa and other regions.

Fact The fastest wind ever measured was a gust of 408 km/h on Barrow Island, Western Australia, during Tropical Cyclone Olivia on 10 April 1996. Faster winds may have occurred inside tornadoes (one Oklahoma tornado in 1999 had Doppler-measured winds of approximately 484 km/h), but tornado winds are not officially counted because they were not measured by a normal weather instrument.

Wind as an energy source

People have used wind energy for over 5,000 years. Sailing ships used wind to cross oceans and explore the world. Windmills were used to grind grain and pump water from at least the 9th century AD. Today, wind turbines are an increasingly important source of clean electricity. As of 2025, wind power produces approximately 9% of the world's electricity and is growing rapidly. The UK gets approximately 25% of its electricity from wind, more than any other major economy.

Did you know? Wind is also important for many plants. Approximately 10% of flowering plants (including most grasses, oaks, birches, hazel and almost all cereal crops) are wind-pollinated. They produce huge amounts of small, light pollen that drifts in the breeze, and they tend to have small dull flowers (no point spending energy attracting insects you do not need). Wind-pollinated plants are responsible for most cases of hay fever.

Deeper dive: how the wind shaped human history

For most of human history, wind was the most important source of energy after human and animal muscle. Whole civilisations rose and fell based on their ability to use wind effectively.

Sailing ships, powered entirely by wind, allowed ancient civilisations to trade across seas: the Phoenicians, Greeks and Romans built empires on Mediterranean trade winds. Later, European powers used the trade winds of the Atlantic to colonise the Americas. The whole Age of Sail (roughly 1500 to 1850) was made possible by sailors who learned to read and use the global wind patterns.

Windmills were equally important. Persian and Arab engineers built the first vertical-axis windmills around 700 to 900 AD. Horizontal-axis windmills appeared in Europe in the 12th century and quickly spread. In the Netherlands, a clever combination of windmills and dykes allowed the Dutch to drain wetlands and create huge areas of new farmland. By 1700, the Netherlands had over 10,000 windmills.

Steam engines took over from wind in the 18th and 19th centuries. But ironically, wind has now returned as one of the most important energy sources of the 21st century. Modern wind turbines are descendants of those old Dutch windmills, but vastly bigger and more efficient. The largest offshore turbines today have blades over 100 metres long and can power approximately 16,000 homes from a single machine. The Hornsea offshore wind farm off the Yorkshire coast is one of the largest in the world and powers over 2 million UK homes.

For more, see air pressure, hurricanes and tornadoes.