A wind forecast becomes useful when you read the mean wind, gusts, direction, time and exposure together. The same numbers may describe a manageable walk along a sheltered street and difficult conditions on a bridge, ridge or open coast.
Mean wind, gusts and direction
Mean wind, sometimes called sustained wind, is the average speed and direction over a defined period. That period is not universal. For surface observations, the UK Met Office uses a ten-minute mean, while the US National Weather Service reports sustained wind as a two-minute average. Tropical-cyclone centres may use one-minute or ten-minute averages. Values from different agencies therefore need the averaging period beside them before they can be compared properly.
A gust is a short-lived peak above the mean. The Met Office defines an observed gust as the highest three-second average in the reporting period. US forecast grids also use a maximum three-second speed, but forecast products may attach that maximum to a particular time or to an interval. “Wind 25 km/h, gusts 45 km/h” means that the general flow is near 25 km/h while brief bursts may reach about 45 km/h. It does not mean that the wind will sit steadily at the higher value.
Wind direction names where the air comes from. A westerly wind blows from west to east. Direction matters because a road, harbour or slope may be exposed to one direction and sheltered from another.
How wind is measured
A cup anemometer derives speed from rotating cups, while a wind vane records direction. Sonic anemometers calculate both from the travel time of sound pulses between sensors.
Standard surface wind measurements are normally made around 10 metres above open, level ground. An ideal site has uniform ground without large obstacles near the mast. Wind usually increases with height near the surface, while trees and buildings slow, divert and churn the flow. A station reading cannot reproduce the wind at every nearby balcony, lane or footpath.
Exposure, terrain and buildings
Ridges and hilltops are often windier than valleys, and air can accelerate over a crest or through a narrow pass. A headland, causeway or open field offers little shelter. In a town, the average wind may be lower, yet corners, gaps between buildings and the downwind side of tall structures can produce turbulent gusts. Trees may shelter one stretch of road and expose a driver to a sudden crosswind at the next gap.
Do not apply a forecast value as a precise measurement at another height. A rooftop terrace, mast or crane can experience different wind from the standard 10-metre level. Likewise, a model grid smooths many small hills and buildings. Airpult’s guide to mountain weather and terrain effects explains other ways that topography changes local conditions.
Wind-speed units
Public forecasts commonly use kilometres per hour (km/h) or miles per hour (mph). Meteorology and science often use metres per second (m/s), while marine and aviation forecasts use knots (kn). The exact conversions are 1 m/s = 3.6 km/h and 1 knot = 1.852 km/h, or about 1.15 mph. Check the unit before comparing apps; a value of 20 means very different conditions in knots and in kilometres per hour.
Reading the Beaufort scale
The Beaufort scale places mean wind into forces from 0 to 12. It remains common in marine forecasts. Useful reference points are:
- Force 0, calm: less than 1 knot.
- Force 4, moderate breeze: 11 to 16 knots.
- Force 6, strong breeze: 22 to 27 knots.
- Force 8, gale: 34 to 40 knots.
- Force 10, storm: 48 to 55 knots.
- Force 12, hurricane force: 64 knots or more.
These bands describe the mean wind, not the highest gust. “Hurricane force” is the name of Force 12; it does not prove that a tropical cyclone is present. The scale’s wave descriptions assume a developed wind sea in open water. Fetch, water depth, swell and the time the wind has been blowing all affect the actual waves, so Beaufort force is not a precise wave or damage forecast for one location.
How to read a wind forecast
First match each value to its hour or forecast period. An hourly mean may describe the value at the displayed time, while a gust may be the strongest value expected during the preceding or following interval. The definition depends on the provider. Daily summaries may hide short peaks, so use the hourly view when timing matters. Our guide to how weather forecasts work explains why values change between model runs and why uncertainty generally grows farther ahead.
Then connect the numbers to the decision:
- Walking or cycling: consider the gust as well as the mean, especially on an exposed route. A crosswind can affect balance more than the same wind from ahead or behind.
- Driving: high-sided vehicles, caravans and motorcycles are more sensitive to gusts. Bridges, viaducts, tunnel exits and gaps in roadside shelter can expose a vehicle suddenly.
- Hills and coasts: check the forecast for the exposed part of the route, not only the town or valley at the start. Wind direction can make a ridge edge or cliff approach more hazardous.
- Boating or work at height: use the specialist marine or site forecast, operating limits and official restrictions. A general public forecast cannot replace them.
There is no single wind speed that is safe for every person, vehicle or activity. The Met Office notes that gusts around 30 to 40 mph can affect balance on exposed mountain ground, but terrain, footing, equipment and experience all change the risk. Use the forecast as one input, not a personal guarantee.
Wind also increases heat loss from exposed skin. Read the wind together with temperature, rain and clothing, or see how it contributes to wind chill and feels-like temperature. For fire weather, wind can spread flames and carry embers, but humidity, fuels and official fire restrictions also matter.
High-wind safety
Official warnings and closures take priority because alert thresholds and likely impacts vary by country and region. Before winds strengthen, bring in or secure loose outdoor objects if it is still safe. During dangerous winds, shelter in a sturdy building and keep away from windows. Avoid trees, scaffolding, damaged structures, exposed coasts and fallen cables. Never touch or approach a downed power line; report it to the local network operator or emergency service.
If you must drive, slow down, leave more room and expect sudden side winds. Do not continue merely because the mean wind looks modest: a warning may account for stronger gusts, vulnerable roads, waves or other hazards that one number does not show.
Wind data in Airpult
Airpult keeps wind speed, gust and bearing as separate model fields. For most sources, it calculates 10-metre wind speed from the horizontal wind components; some sources provide speed directly. Airpult uses a source’s gust field when available. If it is missing, the data pipeline falls back to wind speed, so identical speed and gust values may mean that the source supplied no independent gust estimate.
Airpult does not assign one observation averaging period to every model source. Metric forecasts request SI values in m/s and imperial forecasts request mph. Use Explore to open a location forecast, then read the time step, direction and exposure alongside the numbers.
