Beaufort Scale Page

Beaufort number	Description	Wind speed	Wave height	Sea conditions	Land conditions
0	Calm	< 1 knot < 1 mph < 2 km/h < 0.5 m/s	0 ft (0 m)	Sea like a mirror	Smoke rises vertically.
1	Light air	1-3 knots	0-1 ft	Ripples with appearance of scales are formed, without foam crests	Direction shown by smoke drift but not by wind vanes.
		1-3 mph	0-1 ft
		2-5 km/h	0-0.3 m
		0.5-1.5 m/s	0-0.3 m
2	Light breeze	4-6 knots	1-2 ft	Small wavelets still short but more pronounced; crests have a glassy appearance but do not break	Wind felt on face; leaves rustle; wind vane moved by wind.
		4-7 mph	1-2 ft
		6-11 km/h	0.3-0.6 m
		1.6-3.3 m/s	0.3-0.6 m
3	Gentle breeze	7-10 knots	2-4 ft	Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses	Leaves and small twigs in constant motion; light flags extended.
		8-12 mph	2-4 ft
		12-19 km/h	0.6-1.2 m
		3.4-5.5 m/s	0.6-1.2 m
4	Moderate breeze	11-16 knots	3.5-6 ft	Small waves becoming longer; fairly frequent white horses	Raises dust and loose paper; small branches moved.
		13-18 mph	3.5-6 ft
		20-28 km/h	1-2 m
		5.5-7.9 m/s	1-2 m
5	Fresh breeze	17-21 knots	6-10 ft	Moderate waves taking a more pronounced long form; many white horses are formed; chance of some spray	Small trees in leaf begin to sway; crested wavelets form on inland waters.
		19-24 mph	6-10 ft
		29-38 km/h	2-3 m
		8-10.7 m/s	2-3 m
6	Strong breeze	22-27 knots	9-13 ft	Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray	Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.
		25-31 mph	9-13 ft
		39-49 km/h	3-4 m
		10.8-13.8 m/s	3-4 m
7	High wind, moderate gale, near gale	28-33 knots	13-19 ft	Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind; spindrift begins to be seen	Whole trees in motion; inconvenience felt when walking against the wind.
		32-38 mph	13-19 ft
		50-61 km/h	4-5.5 m
		13.9-17.1 m/s	4-5.5 m
8	Gale, fresh gale	34-40 knots	18-25 ft	Moderately high waves of greater length; edges of crests break into spindrift; foam is blown in well-marked streaks along the direction of the wind	Twigs break off trees; generally impedes progress.
		39-46 mph	18-25 ft
		62-74 km/h	5.5-7.5 m
		17.2-20.7 m/s	5.5-7.5 m
9	Strong/severe gale	41-47 knots	23-32 ft	High waves; dense streaks of foam along the direction of the wind; sea begins to roll; spray affects visibility	Slight structural damage (chimney pots and slates removed).
		47-54 mph	23-32 ft
		75-88 km/h	7-10 m
		20.8-24.4 m/s	7-10 m
10	Storm whole gale	48-55 knots	29-41 ft	Very high waves with long overhanging crests; 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; rolling of the sea becomes heavy; visibility affected	Seldom experienced inland; trees uprooted; considerable structural damage.
		55-63 mph	29-41 ft
		89-102 km/h	9-12.5 m
		24.5-28.4 m/s	9-12.5 m
11	Violent storm	56-63 knots	37-52 ft	Exceptionally high waves; small- and medium-sized ships might be for a long time lost to view behind the waves; sea is covered with long white patches of foam; everywhere the edges of the wave crests are blown into foam; visibility affected	Very rarely experienced; accompanied by widespread damage.
		64-72 mph	37-52 ft
		103-117 km/h	11.5-16 m
		28.5-32.6 m/s	11.5-16 m
12	Hurricane force	≥ 64 knots	≥ 46 ft	The air is filled with foam and spray; sea is completely white with driving spray; visibility very seriously affected	Devastation.
		≥ 73 mph	≥ 46 ft
		≥ 118 km/h	≥ 14 m
		≥ 32.7 m/s	≥ 14 m