Beaufort's Wind Scale

The Beaufort wind scale, which is used to describe the force of the wind, was invented by Admiral Beaufort in 1805. It is divided into a series of values from zero (calm winds) up to twelve and above (hurricanes), with each value representing a specific range and classification of wind velocity.

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Beaufort Number--
Wind Description--
Beaufort No.DescriptionObservationMean Wind Speed (knots)
0CalmSmoke rises vertically. The sea is mirror smooth.0 - 1
1Light AirDirection of wind shown by smoke drift but not by vanes. Scale-like ripples on sea, no foam on wave crests.1 - 3
2Light BreezeWind felt on face, leaves rustle, ordinary vanes moved by wind. Short wavelets, glassy wave crests.4 - 6
3Gentle BreezeLeaves and small twigs in constant motion, wind extends light flag7 - 10
4Moderate BreezeRaises dust and loose paper, small branches moved. Fairly frequent whitecaps occur.11 - 16
5Fresh BreezeSmall trees in leaf begin to sway. Moderate waves, many white foam crests.17 - 21
6Strong BreezeLarge branches in motion, whistling heard in telegraph wires. Some spray on the sea surface.22 - 27
7Moderate (Near) galeWhole trees in motion, inconvenience felt when walking into wind. Foam on waves blows on streaks.28 - 33
8GaleTwigs broken off trees, generally impeded progress. Long streaks on foam appear on sea.34 - 40
9Strong galeStructural damage, e.g. slates and chimney pots removed from roofs. High waves, crests start to roll over.41 - 47
10StormTrees uprooted, considerable structural damage. Exceptionally high waves, visibility affected.48 - 55
11Violent StormWidespread damage56 - 63
12HurricaneAir is filled with spray and foam.> 64