Beaufort Wind Scale - Land and Sea Criteria

Descriptive term	Beaufort scale number	Speed (km/hr)	Speed (knot)	Land criterion	Sea criterion
Calm	0	< 2	< 1	Calm; smoke rises vertically.	Sea like a mirror.
Light	1	2 - 6	1 - 3	Direction of wind shown by smoke drift, but not by wind vanes.	Ripples with the appearance of scales are formed but without foam crests.
Light	2	7 - 12	4 - 6	Wind felt on face; leaves rustle; ordinary vanes moved by wind.	Small wavelets, still short but more pronounced; crests have a glassy appearance and do not break.
Moderate	3	13 - 19	7 - 10	Leaves and small twigs in constant motion; wind extends light flag.	Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses.
Moderate	4	20 - 30	11 - 16	Raises dust and loose paper; small branches are moved.	Small waves, becoming longer; fairly frequent white horses.
Fresh	5	31 - 40	17 - 21	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 (chance of some spray).
Strong	6	41 - 51	22 - 27	Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.	Large waves begin to form; the white foam crests are more extensive everywhere (probably some spray).
Strong	7	52 - 62	28 - 33	Whole trees in motion; inconvenience felt when walking against the wind.	Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind.
Gale	8	63 - 75	34 - 40	Breaks twigs off trees; generally impedes progress.	Moderately high waves of greater length; edges of crests begin to break into spindrift; the foam is blown in well-marked streaks along the direction of the wind.
Gale	9	76 - 87	41 - 47	Slight structural damage occurs.	High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble and roll over; spray may affect visibility.
Storm	10	88 - 103	48 - 55	Seldom experienced inland; trees uprooted; considerable structural damage occurs.	Very high waves with long overhanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy and shocklike; visibility affected.
Storm	11	104 - 117	56 - 63	Very rarely experienced; accompanied by wide-spread damage.	Exceptionally high waves (small and medium-sized ships might be for a time lost to view behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; visibility affected.
Hurricane	12	>= 118	>= 64	Very rarely experienced; accompanied by wide-spread damage.	The air is filled with foam and spray; sea completely white with driving spray; visibility very seriously affected.