You know about Wind Socks. You might be thinking that these orange and white stripes on it are for decoration.
Wait, actually they indicate relative wind speed. Each stripe means 3 knots and indicates a relative wind speed of 1.5 m/s.

• If Wind sock is straight up to first stripe i.e. 3 knots, that indicates a wind speed of 1.5 m/s.
• If Wind sock is straight up to second stripe or 6 knots, that indicates a wind speed of 3 m/s.
• In the same way, 3rd and 4th stripes indicate wind speed of 4.5 and 6 m/s respectively.
• If wind sock is completely straight that indicates a wind speed of 7.5 m/s or above.