Beaufort Wind Scales

Beaufort Wind Scales

Beaufort
number
(force)

Wind Speed

Wave
height
(feet)

WMO*
description

Effects observed on the sea

Effects observed on land

knots

mph

0

under 1

under 1

-

Calm

Sea is like a mirror

Calm. Smoke rises vertically

1

1 - 3

1 - 3

0.25

Light air

Ripples with appearance of scales; no foam crests

Smoke Drift indicates wind direction and wind vanes cease moving

2

4 - 6

4 - 7

0.5 - 1

Light breeze

Small wavelets; crests of glassy appearance, not breaking

Wind felt on exposed skin. Leaves rustle and wind vanes begin to move.

3

7 - 10

8 - 12

2 - 3

Gentle breeze

Large wavelets; crests begin to break; scattered whitecaps

Leaves and small twigs constantly moving, light flags extended.

4

11-16

13-18

3½ - 5

Moderate breeze

Small waves, becoming longer; numerous whitecaps

Dust and loose paper raised. Small branches begin to move.

5

17-21

19-24

6 - 8

Fresh breeze

Moderate waves, taking longer form; many whitecaps; some spray

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

6

22-27

25-31

9½-13

Strong breeze

Larger waves forming; whitecaps everywhere; more spray

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

7

28-33

32-38

13½-19

Near gale

Sea heaps up; white foam from breaking waves begins to be blown in streaks

Whole trees in motion. Effort needed to walk against the wind.

8

34-40

39-46

18-25

Gale

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

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

9

41-47

47-54

23-32

Strong gale

High waves; sea begins to roll; dense streaks of foam; spray may begin to reduce visibility

Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over.

10

48-55

55-63

29-41

Storm

Very high waves with overhanging crests; sea takes white appearance as foam is blown in very dense streaks; rolling is heavy and visibility is reduced

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

11

56-63

64-72

37-52

Violent storm

Exceptionally high waves; sea covered with white foam patches; visibility further reduced

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.

12

64 and over

73 and over

45 and over

Hurricane

Air filled with foam; sea completely white with driving spray; visibility greatly reduced

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

* World Meteorological Organization