Beaufort Scale
| Beaufort Number | Description | Wind speed | Wave height | Sea conditions | Land conditions | ||
| Miles Per Hour | Kilometers Per Hour | Meters | Feet | ||||
| 0 | Calm | < 1 | < 1 | 0 | 0 | Flat. | Calm. Smoke rises vertically. |
| 1 | Light Air | 1 – 3 | 1 – 2 | 0 – 0.2 | 0 – 1 | Ripples without crests. | Wind motion visible in smoke. |
| 2 | Light breeze | 4 – 7 | 3 – 6 | 0.2 – 0.5 | 1 – 2 | Small wavelets. Crests of glassy appearance, not breaking | Wind felt on exposed skin. Leaves rustle. |
| 3 | Gentle breeze | 8 – 12 | 7 – 10 | 0.5 – 1 | 2 – 3.5 | Large wavelets. Crests begin to break; scattered whitecaps | Leaves and smaller twigs in constant motion. |
| 4 | Moderate breeze | 13 – 17 | 11 – 15 | 1 – 2 | 3.5 – 6 | Small waves with breaking crests. Fairly frequent white horses. | Dust and loose paper raised. Small branches begin to move. |
| 5 | Fresh breeze | 18 – 24 | 16 – 20 | 2 – 3 | 6 – 9 | Moderate waves of some length. Many white horses. Small amounts of spray. | Branches of a moderate size move. Small trees begin to sway. |
| 6 | Strong breeze | 25 – 30 | 21 – 26 | 3 – 4 | 9 – 13 | Long waves begin to form. White foam crests are very frequent. Some airborne spray is present. | Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over. |
| 7 | High wind, Moderate gale, Near gale | 31 – 38 | 27 – 33 | 4 – 5.5 | 13 – 19 | Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray. | Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors. |
| 8 | Gale, Fresh gale |
39 – 46 | 34 – 40 | 5.5 – 7.5 | 18 – 25 | Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray. | Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded. |
| 9 | Strong gale | 47 – 54 | 41 – 47 | 7 – 10 | 23 – 32 | High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility. | Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies. |
| 10 | Storm[6], Whole gale |
55 – 63 | 48 – 55 | 9 – 12.5 | 29 – 41 | 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. | Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs. |
| 11 | Violent storm | 64 – 72 | 56 – 63 | 11.5 – 16 | 37 – 52 | 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. | 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. |
| 12 | Hurricane | ≥ 73 | ≥ 64 | ≥ 14 | ≥ 46 | Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility. | Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about. |
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