Beaufort Number *** Wind Speed in Miles/hour (Km/hour) *** Description
- 0 *** <1 (<1.6)***Calm Still: Smoke will rise vertically.
- 1***1-3(1.6-4.8)*** Light Air: Rising smoke drifts, weather vane is
- 2***4-7(6.4-11.3)***Light Breeze: Leaves rustle, can feel wind on
your face, weather vane is inactive.
- 3***8-12(12.9-19.3)***Gentle Breeze: Leaves and twigs move around.
Light weight flags extend.
- 4***13-18 (20.9-29.0)***Moderate Breeze: Moves thin branches,
raises dust and paper.
- 5***19-24 (30.6-38.6)***Fresh Breeze: Moves trees sway.
- 6***25-31(40.2-50.0) ***Strong Breeze: Large tree branches move,
open wires (such as telegraph wires) begin to "whistle", umbrellas
are difficult to keep under control.
- 7***32-38 (51.5-61.2)***Moderate Gale: Large trees begin to sway,
noticeably difficult to walk.
- 8***39-46(62.8-74.0)***Fresh Gale: Twigs and small branches are
broken from trees, walking into the wind is very difficult.
- 9***47-54(75.6-86.9)***Strong Gale: Slight damage occurs to
buildings, shingles are blown off of roofs.
- 10***55-63 (88.5-101.4)***Whole Gale: Large trees are uprooted,
building damage is considerable.
- 11***64-72 (103.0-115.9)***Storm: Extensive widespread damage.
These typically occur only at sea, and rarely inland.
- 12***>73 (>115.9)***Hurricane: Extreme destruction.
NOTE: The Beaufort number is also referred to as a "Force" number,
"Force 10 Gale".
* To calculate knots, divide miles/hour by 1.15.
* Small craft advisories are usually issued when force 6 is reached.
Books on weather and the sea: