What Is Wind Speed?
Wind speed is how fast air is moving horizontally past a given point. It’s reported as a sustained speed: an average over a short period, though the exact averaging window varies by country and context. Gusts are brief spikes above the sustained speed, usually lasting only a few seconds.
Wind speed is measured at a standard height of 10 metres (33 ft) above open ground. Near buildings, trees, or terrain features, actual wind speeds at ground level can differ significantly from the reported value.
Units
Wind speed is reported in different units depending on the region and context:
| Unit | Abbreviation | Used by |
|---|---|---|
| Kilometres per hour | km/h | Most of Europe, general public |
| Metres per second | m/s | Meteorological services, scientific use |
| Miles per hour | mph | UK, US, general public |
| Knots | kn | Aviation, marine, shipping |
To convert roughly: 1 m/s ≈ 3.6 km/h, and 1 knot ≈ 1.85 km/h.
The Beaufort Scale
The Beaufort scale was devised in the early 1800s by Sir Francis Beaufort to describe wind conditions at sea. It’s still widely used to communicate wind strength in practical terms.
| Force | Speed (km/h) | Description | What you’ll notice |
|---|---|---|---|
| 0 | < 1 | Calm | Smoke rises vertically |
| 1 | 1–5 | Light air | Smoke drifts slowly |
| 2 | 6–11 | Light breeze | Leaves rustle, you feel wind on your face |
| 3 | 12–19 | Gentle breeze | Leaves and small twigs move, flags begin to extend |
| 4 | 20–28 | Moderate breeze | Raises dust and loose paper, small branches move |
| 5 | 29–38 | Fresh breeze | Small trees sway, wavelets form on lakes |
| 6 | 39–49 | Strong breeze | Large branches move, umbrellas difficult to use |
| 7 | 50–61 | Near gale | Whole trees sway, walking against wind is difficult |
| 8 | 62–74 | Gale | Twigs break off trees, walking is hard |
| 9 | 75–88 | Strong gale | Chimney pots and roof slates removed, slight structural damage |
| 10 | 89–102 | Storm | Trees uprooted, significant structural damage |
| 11 | 103–117 | Violent storm | Widespread damage |
| 12 | 118+ | Hurricane | Devastating damage |
How Wind Is Measured
The most common instrument is an anemometer, a device with spinning cups or a rotating vane mounted on a mast. As wind turns the cups, the rotation speed is converted to wind speed. Modern weather stations use ultrasonic anemometers that have no moving parts; they measure the time it takes sound pulses to travel between sensors, which changes with wind speed and direction.
Weather stations also record wind direction: the compass direction the wind is coming from. A “westerly” wind blows from the west towards the east.
Gusts vs. Sustained Wind
A forecast might say “wind 25 km/h, gusts to 45 km/h.” The sustained speed tells you the general conditions. The gust speed tells you the peak: the strongest bursts you might experience. Gusts are caused by turbulence, terrain effects, and convection. They’re particularly relevant for driving, cycling, and anything involving balance or loose objects.
In storms, the gust speed can be double the sustained speed or more.
Why Wind Matters
Wind affects far more than comfort:
- Feels like temperature: Wind strips heat from your body. A moderate breeze in cold weather can make it feel several degrees colder (wind chill).
- Air quality: Wind disperses pollutants. Calm days with low wind tend to have worse air quality, especially in cities.
- Pollen: Dry, windy days carry more pollen over longer distances.
- Fire risk: Strong winds spread wildfires rapidly and make them harder to control.
- Travel: High winds affect cycling, high-sided vehicles, bridges, and ferry crossings. Airlines may divert or delay flights in strong crosswinds.
How Airpult Shows Wind
On Airpult, wind speed and direction are shown on the forecast page alongside temperature and conditions. You can see both the sustained speed and gust speed where available. Use the explore page to search for any location and check its wind forecast.
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