| Beaufort number |
Wind speed |
Mean wind speed (kt / km/h / mph) |
Description |
Wave height |
Sea
conditions |
Land
conditions |
| kt |
km/h |
mph |
m/s |
m |
ft |
| 0 |
0 |
0 |
0 |
0-0.2 |
0 / 0 / 0 |
Calm |
0 |
0 |
Flat. |
Calm. Smoke rises vertically. |
| 1 |
1-3 |
1-6 |
1-3 |
0.3-1.5 |
2 / 4 / 2 |
Light air |
0.1 |
0.33 |
Ripples without crests. |
Wind motion visible in smoke. |
| 2 |
4-6 |
7-11 |
4-7 |
1.6-3.3 |
5 / 9 / 6 |
Light breeze |
0.2 |
0.66 |
Small wavelets. Crests of glassy appearance, not breaking |
Wind felt on exposed skin. Leaves rustle. |
| 3 |
7-10 |
12-19 |
8-12 |
3.4-5.4 |
9 / 17 / 11 |
Gentle breeze |
0.6 |
2 |
Large wavelets. Crests begin to break; scattered whitecaps |
Leaves and smaller twigs in constant motion. |
| 4 |
11-16 |
20-29 |
13-18 |
5.5-7.9 |
13 / 24 / 15 |
Moderate breeze |
1 |
3.3 |
Small waves. |
Dust and loose paper raised. Small branches begin to move. |
| 5 |
17-21 |
30-39 |
19-24 |
8.0-10.7 |
19 / 35 / 22 |
Fresh breeze |
2 |
6.6 |
Moderate (1.2 m) longer waves. Some foam and spray. |
Smaller trees sway. |
| 6 |
22-27 |
40-50 |
25-31 |
10.8-13.8 |
24 / 44 / 27 |
Strong breeze |
3 |
9.9 |
Large waves with foam crests and some spray. |
Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. |
| 7 |
28-33 |
51-62 |
32-38 |
13.9-17.1 |
30 / 56 / 35 |
Near gale |
4 |
13.1 |
Sea heaps up and foam begins to streak. |
Whole trees in motion. Effort needed to walk against the wind. |
| 8 |
34-40 |
63-75 |
39-46 |
17.2-20.7 |
37 / 68 / 42 |
Gale |
5.5 |
18 |
Moderately high waves with breaking crests forming spindrift. Streaks of foam. |
Twigs broken from trees. Cars veer on road. |
| 9 |
41-47 |
76-87 |
47-54 |
20.8-24.4 |
44 / 81 / 50 |
Strong gale |
7 |
23 |
High waves (2.75 m) with dense foam. Wave crests start to roll over. Considerable spray. |
Light structure damage. |
| 10 |
48-55 |
88-102 |
55-63 |
24.5-28.4 |
52 / 96 / 60 |
Storm |
9 |
29.5 |
Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced. |
Trees uprooted. Considerable structural damage. |
| 11 |
56-63 |
103-117 |
64-72 |
28.5-32.6 |
60 / 111 / 69 |
Violent storm |
11.5 |
37.7 |
Exceptionally high waves. |
Widespread structural damage. |
| 12 |
>63 |
>117 |
>72 |
>32.7 |
N/A |
Hurricane |
14+ |
46+ |
Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility very greatly reduced. |
Considerable and widespread damage to structures. |
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