Wind speed (Motion)

Wind speed, or wind velocity, is a fundamental atmospheric rate. Wind speed affects weather forecasting, aircraft and maritime operations, construction projects, growth and metabolism rate of many plant species, and countless other implications. Wind speed is now commonly measured with an anemometer but can also be classified using the older Beaufort scale which is based on people's observation of specifically defined wind effects.

Description
Beaufort number	0	1	2	3	4	5	6	7	8	9	10	11	12
Description	Calm	Light air	Light breeze	Gentle breeze	Moderate breeze	Fresh breeze	Strong breeze	High wind	Gale	Strong gale	Storm	Violent storm	Hurricane force
Sea conditions	Flat.	Ripples without crests.	Small wavelets. Crests of glassy appearance, not breaking	Large wavelets. Crests begin to break; scattered whitecaps	Small waves with breaking crests. Fairly frequent white horses.	Moderate waves of some length. Many white horses. Small amounts of spray.	Long waves begin to form. White foam crests are very frequent. Some airborne spray is present.	Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray.	Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray.	High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility.	Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility.	Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility.	Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility.
Land conditions	Calm. Smoke rises vertically.	Smoke drift indicates wind direction, still wind vanes.	Wind felt on exposed skin. Leaves rustle, vanes begin to move.	Leaves and small twigs constantly moving, light flags extended.	Dust and loose paper raised. Small branches begin to move.	Branches of a moderate size move. Small trees in leaf begin to sway.	Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over.	Whole trees in motion. Effort needed to walk against the wind.	Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.	Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over.	Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs.	Widespread damage to vegetation. Many roofing surfaces are damaged; asphalt tiles that have curled up and/or fractured due to age may break away completely.	Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about.
Wind speed
Kilometres per hour (min)	0	1.1	5.6	12	20	29	39	50	62	75	89	103	118
Kilometres per hour (max)	1	5.5	11	19	28	38	49	61	74	88	102	117	200
Miles per hour (min)	0	1	4	8	13	18	25	31	39	47	55	64	73
Miles per hour (max)	1	3	7	12	17	24	30	38	46	54	63	72	100
Knot (min)	0	1	3	7	11	16	21	27	34	41	48	56	64
Knot (max)	1	2	6	10	15	20	26	33	40	47	55	63	100
Metre per second (min)	0	0.3	1.6	3.4	5.5	8.0	10.8	13.9	17.2	20.8	24.5	28.5	32.7
Metre per second (max)	0.3	1.5	3.4	5.4	7.9	10.7	13.8	17.1	20.7	24.4	28.4	32.6	50
Wave height
Metre (min)	0	0.01	0.2	0.5	1	2	3	4	5.5	7	9	11.5	14
Metre (max)	0	0.2	0.5	1	2	3	4	5.5	7.5	10	12.5	16	20
Foot (min)	0	0.01	1	2	3.5	6	9	13	18	23	29	37	46
Foot (max)	0	1	2	3.5	6	9	13	19	25	32	41	52	100