The Beaufort Wind-Speed Scale
Strength Speed (km/h) Effect
0 Calm 0 Smoke rises vertically
1 Light air 1 Smoke drifts slowly
2 Light breeze 6 Leaves rustle
3 Gentle breeze 12 Flags fly upright
4 Moderate breeze 20 Dust blows up
5 Fresh breeze 30 Small trees sway
6 Strong breeze 40 Large branches sway
7 Near gale 51 Walking difficult
8 Gale 62 Twigs break from trees
9 Strong gale 75 Roof tiles dislodged
10 Storm 88 Trees uproot
11 Violent storm 102 Widespread damage
12 Hurricane 120+ Large scale devastation