How windy is it?


Beaufort scale number

Descriptive term

Units in km/h

Units in knots

Description on Land

Description at Sea

0

Calm

0

0

Smoke rises vertically

Sea like a mirror.

1-3

Light winds

19 km/h or less

10 knots or less

Wind felt on face; leaves rustle; ordinary vanes moved by wind.

Small wavelets, ripples formed but do not break: A glassy appearance maintained.

4

Moderate winds

20 - 29 km/h

11-16 knots

Raises dust and loose paper; small branches are moved.

Small waves - becoming longer; fairly frequent white horses.

5

Fresh winds

30 - 39 km/h

17-21 knots

Small trees in leaf begin to sway; crested wavelets form on inland waters

Moderate waves, taking a more pronounced long form; many white horses are formed - a chance of some spray

6

Strong winds

40 - 50 km/h

22-27 knots

Large branches in motion; whistling heard in telephone wires; umbrellas used with difficulty.

Large waves begin to form; the white foam crests are more extensive with probably some spray

7

Near gale

51 - 62 km/h

28-33 knots

Whole trees in motion; inconvenience felt when walking against wind.

Sea heaps up and white foam from breaking waves begins to be blown in streaks along direction of wind.

8

Gale

63 - 75 km/h

34-40 knots

Twigs break off trees; progress generally impeded.

Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks along the direction of the wind.

9

Strong gale

76 - 87 km/h

41-47 knots

Slight structural damage occurs -roofing dislodged; larger branches break off.

High waves; dense streaks of foam; crests of waves begin to topple, tumble and roll over; spray may affect visibility.

10

Storm

88 - 102 km/h

48-55 knots

Seldom experienced inland; trees uprooted; considerable structural damage.

Very high waves with long overhanging crests; the resulting foam in great patches is blown in dense white streaks; the surface of the sea takes on a white appearance; the tumbling of the sea becomes heavy with visibility affected.

11

Violent storm

103 -117 km/h

56-63 knots

Very rarely experienced - widespread damage

Exceptionally high waves; small and medium sized ships occasionally lost from view behind waves; the sea is completely covered with long white patches of foam; the edges of wave crests are blown into froth.

12+

Hurricane

118 km/h or more

64 knots or more

Very rarely experienced - widespread damage

The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected


(from the Australian Bureau of Meteorology)