How to read a windsock

Windsocks are a familiar sight at all airports accross the globe. But do most people know why they are made and coloured the way they are.  The wite and red stripes are not for visibilty. Although the choice of colour of red or orange is recommended by ICAO for visibilty. The stripes are actually used for pilots to give an indication of wind speed. Each stripe adds up 3 knots to the estimated wind speed. A fully extended windsock suggests a wind speed of 15 knots (28 km/h; 17 mph) or greater. So the indicated wind speeds will be either 3kts, 6kts, 9kts, 12kts or 15kts or greater.