Wind Speed

Wind Speed:
Beaufort

Number

Description Wind Speed Land Conditions Sea Conditions
0 Calm < 1 km/h Calm. Smoke rises vertically. Flat. Wave Height 0m.
1 Light Air 1.1 – 5.5 km/h Smoke drift indicates wind direction.
Wind vanes cease moving.
Ripples without crests.  Wave height 0 – 0.2m.
2 Light Breeze 5.6 – 11 km/h Wind felt on exposed skin.
Leaves rustle and wind vanes begin to move.
Small wavelets. Crests of glossy appearance, not breaking. Wave height 0.2 – 0.5m.
3 Gentle Breeze 12 – 19 km/h Leaves and small twigs constantly moving, light flags extended. Large wavelets. Crests begin to break, scattered whitecaps. Wave height 0.5 – 1m.
4 Moderate Breeze 20 – 28 km/h Dust and loose paper raised. Small branches begin to move. Small waves with breaking crests. Fairly frequent whitecaps. Wave height 1 – 2m.
5 Fresh Breeze 29 – 38 km/h Branches if a moderate size move.  Small trees in leaf begin to sway. Moderate waves of some length. Many whitecaps. Small amounts of spray. Wave height 2 – 3m.
6 Strong Breeze 39 – 49 km/h Large branches in motion. whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cants tip over. Long waves begin to form. White foam crests are very frequent. Some airborne spray is present. Wave height 3 – 4m.
7 High Wind, Moderate Gale, Near Gale 50 – 61 km/h Whole trees in motion. Effort needed to walk against the wind. Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction.  Moderate amounts of airborne spray. Wave height 4 – 5.5m
The Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale. The scale was devised in 1805 by Francis Beaufort (later Rear Admiral Sir Francis Beaufort), an Irish-born Royal Navy officer, while serving on HMS Woolwich. It was officially adopted in the 1830’s and was first used during Darwin’s voyage on HMS Beagle. The complete scale extends to Force 12 which is well in excess of the safe kite flying range.