Wind takes two measurements, speed and direction, and it is by far the most exposure-sensitive element in meteorology. Move an anemometer three metres and the readings change. Put it in the lee of a building and you can halve them. Everything below matters more for wind than for any other measurement, because a badly sited wind sensor is not slightly wrong, it is measuring something else entirely.
This section covers fixed anemometers and the wind sensors built into complete stations, handheld meters for spot readings on site, and the professional instruments used in shooting, motorsport, ballooning, ventilation testing and fire service work.
How wind speed is measured
The classic instrument is the three-cup anemometer. Three hemispherical cups on horizontal arms catch more drag on their concave face than their convex one, so the assembly always turns the same way regardless of wind direction, and its rotation rate is very nearly proportional to wind speed. A magnet and reed switch or an optical chopper counts revolutions and the electronics convert that to a speed. Three cups rather than four turn out to give a more linear response.
Direction is measured separately by a vane, which points into wind and turns a potentiometer or an array of magnetic sensors to give a bearing, conventionally reported as the direction the wind is coming from.
Ultrasonic anemometers have no moving parts at all. They send sound pulses between fixed transducers and measure how much the wind speeds up or slows down the flight time along each path, deriving both speed and direction from the differences. They cost more but never wear out, respond instantly, and are the choice where servicing a mast is difficult.
Handheld meters usually use a small impeller rather than cups, and vane or hot-wire meters measure air velocity in ducts and vents. A hot-wire sensor holds a fine heated wire at constant temperature and measures the power needed to do so, since moving air cools it — which makes it excellent at very low airflows where an impeller will not turn.
Mounting height and exposure
The international reference height is 10 metres above open ground, and every published wind statistic assumes it. That is because wind speed increases with height in a predictable curve as ground friction falls away, so a sensor at 2 metres reads substantially lower than the same sensor at 10.
Exposure matters as much as height. The working rule is that the sensor should be at least ten times the height of the nearest obstruction away from it — so a 6-metre tree means 60 metres of clearance for a genuinely representative reading. Very few domestic sites can achieve that, and the practical answer is to get the sensor as high and as clear as you can, ideally above the roofline, and then treat your figures as consistent rather than absolute. Consistency is enough for almost everything: you will still see accurately when it is windier than last week.
Gust versus mean, and why both appear
Wind is turbulent, so a single instantaneous number is meaningless. The convention is to report a mean speed averaged over ten minutes alongside the peak gust, defined as the highest three-second average within that period. Gusts commonly run 1.5 to 2 times the mean.
Which one you need depends on the job. Mean speed is what matters for ventilation calculation, wind energy assessment and climatology. Gust is what matters for safety: lifting operations, marquees, scaffolding, cranes and site closure decisions are all made on peak gust, because it is the gust that does the damage.
Units, and the Beaufort scale
The same wind gets quoted four ways. Metres per second is the scientific standard, knots are used at sea and in aviation, miles per hour is the UK public convention, and kilometres per hour is used across most of Europe. Ten metres per second is roughly 19.4 knots, 22.4 mph or 36 km/h. Most instruments switch between all four. The Beaufort scale is not a unit but a descriptive band — force 4 is a moderate breeze at 11 to 16 knots, force 8 a gale at 34 to 40 — and it remains genuinely useful because it is defined by observable effects rather than by numbers.
What we recommend
For spot readings, the Technoline EA3000 Mini Anemometer is the pocket option and the Technoline EA3010 Mini Anemometer with Temperature adds a thermometer. The Digital Anemometer for Wind Speed & Temperature and Portable Digital Anemometer measuring air velocity, temperature and humidity suit ventilation and airflow work, and the Portable Digital Anemometer with USB logs to a computer. For professional handheld use the Kestrel 5000 with wind speed, temperature, humidity and pressure is the reference instrument.
For a fixed installation, the ACCUR8 DWS7100 7-in-1 Solar-Powered WiFi Weather Station and TechnoLine WS 2816 Complete Weather Station cover domestic use, the Davis Wireless Vantage Pro2 is the enthusiast and semi-professional standard with a separable anemometer that can be mounted high while the rest of the suite stays low, and the RainWise MK-III Long Range Weather Station Sensor Assembly is built for exposed and remote professional sites.
Related measurements
Handheld instruments are grouped in Handheld Anemometers, Kestrel Wind Meters and Handheld Weather Stations. Fixed systems are in Weather Stations, Professional Weather Stations and RainWise. Because wind chill needs temperature and gust alarms need pressure, see Temperature and Storm & Lightning. Replacement cups, vanes and mounting hardware are in Sensors, Spares & Accessories and Mounting Poles & Tripods, logging is in Data Loggers, and the other elements are indexed under Elements.