| beaufort number |
wind speed (mph/knots) |
description |
effect at sea |
effect on land |
| 0 |
<1 / <1 |
calm |
water is mirror-like |
still, calm air, smoke rises vertically |
| 1 |
1-3 / 1-3 |
light air |
small ripples appear on water surface |
rising smoke drifts, wind vane is inactive |
| 2 |
4-7 / 4-6 |
light breeze |
small wavelets develop, crests are glassy |
leaves rustle, can feel wind on your face, wind vanes begin to move |
| 3 |
8-12 / 7-10 |
gentle breeze |
large wavelets, crests start to break, some whitecaps |
leaves and small twigs move, light weight flags extend |
| 4 |
13-18 / 11-16 |
moderate breeze |
small waves develop, becoming longer, whitecaps |
small branches move, raises dust, leaves and paper |
| 5 |
19-24 / 17-21 |
fresh breeze |
white crested wavelets form, some spray |
small trees sway |
| 6 |
25-31 / 22-27 |
strong breeze |
larger waves form, whitecaps prevalent, spray |
large tree branches move, telephone wires begin to "whistle", umbrellas are difficult to keep under control |
| 7 |
32-38 / 28-33 |
moderate or near gale |
larger waves develop, white foam from breaking waves begins to be blown |
large trees sway, becoming difficult to walk |
| 8 |
39-46 / 34-40 |
gale or fresh gale |
moderately large waves with blown foam |
twigs and small branches are broken from trees, walking is difficult |
| 9 |
47-54 / 41-47 |
strong gale |
high waves (6 meters), rolling seas, dense foam, blowing spray reduces visibility |
slight damage occurs to buildings, shingles are blown off of roofs |
| 10 |
55-63 / 48-55 |
whole gale or storm |
large waves (6-9 meters), overhanging crests, sea becomes white with foam, heavy rolling, reduced visibility |
trees are broken or uprooted, building damage is considerable |
| 11 |
64-72 / 56-63 |
violent storm |
large waves (9-14 meters), white foam, visibility further reduced |
extensive widespread damage |
| 12 |
73+ / 64+ |
hurricane |
large waves over 14 meters
(46 ft), air filled with foam, sea white with foam and driving spray, little visibility |
extreme destruction, devastation |
