| Beaufort scale number |
Descriptive term |
Units in km/h |
Units in knots |
Description on Land |
Description at Sea |
| 0 |
Calm |
0 |
0 |
Smoke rises vertically |
Sea like a mirror. |
| 1-3 |
Light winds |
19 km/h or less |
10 knots or less |
Wind felt on face; leaves rustle; ordinary vanes moved by wind. |
Small wavelets, ripples formed but do not break: A glassy appearance maintained. |
| 4 |
Moderate winds |
20 - 29 km/h |
11-16 knots |
Raises dust and loose paper; small branches are moved. |
Small waves - becoming longer; fairly frequent white horses. |
| 5 |
Fresh winds |
30 - 39 km/h |
17-21 knots |
Small trees in leaf begin to sway; crested wavelets form on inland waters |
Moderate waves, taking a more pronounced long form; many white horses are formed - a chance of some spray |
| 6 |
Strong winds |
40 - 50 km/h |
22-27 knots |
Large branches in motion; whistling heard in telephone wires; umbrellas used with difficulty. |
Large waves begin to form; the white foam crests are more extensive with probably some spray |
| 7 |
Near gale |
51 - 62 km/h |
28-33 knots |
Whole trees in motion; inconvenience felt when walking against wind. |
Sea heaps up and white foam from breaking waves begins to be blown in streaks along direction of wind. |
| 8 |
Gale |
63 - 75 km/h |
34-40 knots |
Twigs break off trees; progress generally impeded. |
Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks along the direction of the wind. |
| 9 |
Strong gale |
76 - 87 km/h |
41-47 knots |
Slight structural damage occurs -roofing dislodged; larger branches break off. |
High waves; dense streaks of foam; crests of waves begin to topple, tumble and roll over; spray may affect visibility. |
| 10 |
Storm |
88 - 102 km/h |
48-55 knots |
Seldom experienced inland; trees uprooted; considerable structural damage. |
Very high waves with long overhanging crests; the resulting foam in great patches is blown in dense white streaks; the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy with visibility affected. |
| 11 |
Violent storm |
103 -117 km/h |
56-63 knots |
Very rarely experienced - widespread damage |
Exceptionally high waves; small and medium sized ships occasionally lost from view behind waves; the sea is completely covered with long white patches of foam; the edges of wave crests are blown into froth. |
| 12+ |
Hurricane |
118 km/h or more |
64 knots or more |
The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected |