Beaufort Scale (Wind Speed)
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Etymology: Sir Francis Beaufort: a scale in which the force of the wind is indicated by numbers from 0 to 12.
| BEAUFORT NUMBER |
NAME | WIND SPEED MPH |
WIND SPEED KPH |
DESCRIPTION |
| 0 | calm | <1 | <1 | calm; smoke rises vertically |
| 1 | light air | 1-3 | 1-5 | direction of wind shown by smoke but not by wind vanes |
| 2 | light breeze | 4-7 | 6-11 | wind felt on face; leaves rustle; wind vane moves |
| 3 | gentle breeze | 8-12 | 12-19 | leaves and small twigs in constant motion; wind extends light flag |
| 4 | moderate breeze | 13-18 | 20-28 | wind raises dust and loose paper; small branches move |
| 5 | fresh breeze | 19-24 | 29-38 | small-leaved trees begin to sway; crested wavelets form on inland waters |
| 6 | strong breeze | 25-31 | 39-49 | large branches move; overhead wires whistle; umbrellas difficult to control |
| 7 | moderate gale or near gale | 32-38 | 50-61 | whole trees sway; walking against wind is difficult |
| 8 | fresh gale or gale | 39-46 | 62-74 | twigs break off trees; moving cars veer |
| 9 | strong gale | 47-54 | 75-88 | slight structural damage occurs; shingles may blow away |
| 10 | whole gale or storm | 55-63 | 89-102 | trees uprooted; considerable structural damage occurs |
| 11 | storm or violent storm | 64-72 | 103-117 | widespread damage occurs |
| 12 | hurricane* | 72> | 117> | widespread damage occurs |
*The U.S. uses 74 statute mph as the speed criterion for a hurricane.
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