BEAUFORT SCALE
Observable EffectsInternational DescriptionBeaufort NumberWind Speed
meters/sec
m/s
km/hour
km/h
miles/hour
mph
knots
kt
Air calm; smoke rises verticallyCalm0< 0.5< 1< 1< 1
Direction of wind shown by smoke drift but not by wind vanesLight Air10.5-1.51-51-31-3
Wind felt on face; leaves rustle; wind vanes moved by windLight Breeze22-36-114-74-6
Leaves and small twigs in continual motion; wind extends light flagsGentle Breeze34-512-198-127-10
Raises dust, loose paper; moves small branchesModerate Breeze46-820-2913-1811-15
Small trees in leaf begin to sway; white crested wavelets form on inland watersFresh Breeze59-1030-3919-2416-21
Large branches in motion; umbrellas used with difficulty; telephone wires "whistle"Strong Breeze611-1340-5025-3122-27
Whole trees in motion; inconvenience felt walking against windModerate or Near Gale714-1751-6132-3828-33
Breaks twigs off trees; wind generally impedes progressGale or Fresh Gale818-2062-7439-4634-40
Slight structural damage occursStrong Gale921-2475-8747-5441-47
trees uprooted; considerable structural damage occursWhole Gale or Storm1025-2888-10155-6348-55
Widespread damageViolent Storm1129-33102-11864-7356-63
DevastationHurricane12> 33> 118> 73> 64
[ 1 mile = 1609 m ]   [ 1 nautical mile = 1852 m ]   [ 1 knot = 1 nautical mile per hour ]