The Beaufort Scale or Beaufort Wind Force Scale is a system for estimating wind speed featured in our Weather Stations. This universal measuring system is based on the effects wind has on the physical environment. Rated on a 13 point scale from 0 (calm) to 12 (hurricane levels of wind damage).
0 – Calm
- Wind speeds: less than 1 knot
(<1km/h; <0.3 m/s) - Sea/Coastal Areas: Sea is calm and flat
- Sea disturbance number: 0
- Probable wave height: flat (0ft)
- On land: Smoke rises vertically
1 – Light Air
- Wind speeds: 1 – 3 knots
(1-5km/h; 0.3 – 1.5m/s) - Sea/Coastal Areas: Ripples can be seen and potential small wavelets, but with no foam
- Sea disturbance number: 0
- Probable wave height: 0 – 0.1m (0ft)
- On land: Direction of wind shown by smoke drift, but not by vanes
2 – Light Breeze
- Wind speeds: 4 – 6 knots
(6 – 11km/h; 1.6 – 3.3m/s) - Sea/Coastal Areas: Small wavelets, still short but more pronounced; crests have a glassy appearance and do not break
- Sea disturbance number: 1
- Probable wave height: 0 – 0.3m (0 – 1ft)
- On land: Wind felt on face; leaves rustle; ordinary vane moved by wind
3 – Gentle Breeze
- Wind speeds: 7-10 knots
(12 – 19km/h; 3.4 – 5.4m/s) - Sea/Coastal Areas: Large wavelets and crests begin to break. Foam of glassy appearance; perhaps scattered white horses
- Sea disturbance number: 3
- Probable wave height: 0.3 – 0.6m (1 – 2ft)
- On land: Leaves and small twigs in constant motion
4 – Moderate Breeze
- Wind speeds: 11-16 knots
(20 – 28km/h; 5.5 – 7.9m/s) - Sea/Coastal Areas: Small waves, becoming longer; fairly frequent white horses
- Sea disturbance number: 3
- Probable wave height: 1m (3.5ft)
- On land: Raises dust and loose paper; small branches are moved
5 – Fresh Breeze
- Wind speeds: 17 – 21 knots
(29 – 38km/h; 8.0 – 10.7m/s) - Sea/Coastal Areas: Moderate waves taking a more pronounced long form. Many white horses are formed and chances of some spray
- Sea disturbance number: 4
- Probable wave height: 2m (6 – 7ft)
- On land: Small trees with foliage begin to sway; crested wavelets form on inland waters
6 – Strong Breeze
- Wind speeds: 22 – 27 knots
(39 – 49km/h; 10.8 – 13.8m/s) - Sea/Coastal Areas: Large waves begin to form; the white foam crests are more extensive everywhere; probably some spray
- Sea disturbance number: 5
- Probable wave height: 3m (9 – 10ft)
- On land: Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty
7 – Near Gale / Moderate Gale
- Wind speeds: 28 – 33 knots
(50 – 61km/h; 13.9 – 17.1m/s) - Sea/Coastal Areas: Sea heaps up and white foam from the breaking waves begins to be blown in streaks along the direction of the wind
- Sea disturbance number: 6
- Probable wave height: 4m (13 – 14ft)
- On land: Whole trees in motion; inconvenience felt when walking against wind
8 – Gale / Fresh Gale
- Wind speeds: 34 – 40 knots
(62 – 74km/h; 17.2 – 20.7m/s) - Sea/Coastal Areas: Moderately high waves of greater length; edges crests begin to break into spindrift; the foam is blown in well-marked streaks along the direction of the wind
- Sea disturbance number: 6
- Probable wave height: 5.5m (18ft)
- On land: Breaks twigs off trees
9 – Strong Gale
- Wind speeds: 41 – 47 knots
(75 – 88km/h; 20.8 – 24.4m/s) - Sea/Coastal Areas: High waves; dense streaks of foam along the direction of wind; crests of waves begin to topple, tumble and roll over
- Sea disturbance number: 6
- Probable wave height: 7m (23ft)
- On land: Slight structural damage occurs (chimney post and slates removed)
10 – Storm / Whole Gale
- Wind speeds: 48 – 55 knots
(89 – 102km/h; 24.5 – 28.4m/s) - Sea/Coastal Areas: Very high waves with long overhanging crests; resulting foam in great patches is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes a white appearance; tumbling of the sea becomes heavy and shock-like
- Sea disturbance number: 7
- Probable wave height: 9m (29ft)
- On land: Seldom experienced inland; trees uprooted; considerable structural damage occurs
11 – Violent Storm
- Wind speeds: 56 – 63 knots
- (103 – 117km/h; 28.5 – 32.6m/s)
- Sea/Coastal Areas: Exceptionally high waves; sea is completely covered with long white patches of foam lying along the direction of wind; everywhere the edges are blown into froth
- Sea disturbance number: 8
- Probable wave height: 11m (37ft)
- On land: Very rarely experienced; accompanied by widespread damage
12 – Hurricane
- Wind speeds: 64 knots and greater
(>117km/h; >32.7m/s) - Sea/Coastal Areas: The air is filled with foam and spray; sea completely white with driving spray
- Sea disturbance number: 9
- Probable wave height: 11m and greater (>37ft)
- On land: Very rarely experienced; accompanied by widespread damage
