| 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 |