Beaufort Number

Description

Wind Speed

Wave Height

Sea Conditions

Land Conditions

mph

km/h

kts

m

ft

Calm

< 1

< 1

< 1

0

0

Flat

Calm. Smoke rises vertically

Light air

1 - 3

1.1 - 5.5

1 - 2

0 - 0.2

0 - 1

Ripples without crests

Wind motion visible in smoke

Light breeze

4 - 7

5.6 - 11

3 - 6

0.2 - 0.5

1 - 2

Small wavelets. Crests of glassy appearance, not breaking

Wind felt on exposed skin. Leaves rustle

Gentle breeze

8 - 12

12 - 19

7 - 10

0.5 - 1

2 - 3.5

Large wavelets. Crests begin to break; scattered whitecaps

Leaves and smaller twigs in constant motion

Moderate breeze

13 - 17

20 - 28

11 - 15

1 - 2

3.5 - 6

Small waves with breaking crests. Fairly frequent white horses

Dust and loose paper raised. Small branches begin to move

Fresh breeze

18 - 24

29 - 38

16 - 20

2 - 3

6 - 9

Moderate waves of some length. Many white horses. Small amounts of spray

Branches of a moderate size move. Small trees begin to sway

Strong breeze

25 - 30

39 - 49

21 - 26

3 - 4

9 - 13

Long waves begin to form. White foam crests are very frequent. Some airborne spray is present

Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic rubbish bins tip over

High wind, moderate gale, near gale

31 - 38

50 - 61

27 - 33

4 - 5.5

13 - 19

Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray

Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors.

Gale, fresh gale

39 - 46

62 - 74

34 - 40

5.5 - 7.5

17.2 - 20.7

Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray

Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded

Strong gale

47 - 54

75 - 88

41 - 47

7 - 10

23 - 32

High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility

Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies

Storm, whole gale

55 - 63

89 - 102

48 - 55

9 - 12.5

29 - 41

Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility

Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs

Violent storm

64 - 72

103 - 117

56 - 63

11.5 - 16

37 - 52

Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility

Widespread damage to vegetation. Many roofing surfaces are damaged; asphalt tiles that have curled up and/or fractured due to age may break away completely

Hurricane

>73

>118

>64

>14

>46

Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility

Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about