Winds on the Beaufort scale

Wind Designation From Winds Effect
km/h m/s Knots mph
0 Calm < 1 < 0,3 < 1 < 1 Nothing
1 Light air 1 - 5 0,3 - 1,5 1 - 3 1 - 3 Diversion of smoke
2 Light breeze 6 - 11 1,6 - 3,3 4 - 6 4 - 7 Contractions of leaves
3 Gentle breeze 12 - 19 3,4 - 5,4 7 - 10 8 - 12 Movement of branches
4 Moderate breeze 20 - 28 5,5 - 7,9 11 - 15 13 - 17 Movement of limbs
5 Fresh breeze 29 - 38 8,0 - 10,7 16 - 21 18 - 24 Movement of small trees
6 Strong breeze 39 - 49 10,8 - 13,8 22 - 27 25 - 30 Movement strong branches
7 High wind 50 - 61 13,9 - 17,1 28 - 33 31 - 38 Movement of trees
8 Gale 62 - 74 17,2 - 20,7 34 - 40 39 - 46 Difficulty in walking
9 String gale 75 - 88 20,8 - 24,4 41 - 47 47 - 54 House damage
10 Storm 89 - 102 24,5 - 28,4 48 - 55 55 - 63 Uprooting of trees
11 Violent storm 103 - 117 28,5 - 32,6 56 - 63 64 - 73 Storm damage
12 Hurricane > 118 > 32,7 > 64 > 74 Devastation

The Beaufort scale is the most popular scale to name and rate winds by the wind speed.
The scale is named after Sir Francis Beaufort, even he did not much for the history of it. If a wind strength is given without an addendum, the Beaufort scale is used. In the weather forecast and journals this scale is used.

The current version of this scale got defined with 13 winds in 1970. The winds are from 0 up to 12. With the wind speed in km/h or knots, you can asign the wind speed to a wind strength.

In the year 1949 there was a extension for the scale. It has 5 more winds. So there existed 18 winds for a time. In this scale the wind strength 17 was the last. This variant is not used anymore.