Beau-
fort
grade

Description

Average wind speed at a height of 10m over open terrain

Examples of the effects of wind in inland areas

m/s

km/h

0

Calm

0 - 0,2

< 1

Smoke rises vertically

1

Light air

0,3 - 1,5

1 - 5

Direction shown by smoke drift but not by wind vane

2

Light breeze

1,6 - 3,3

6 - 11

Wind felt on face; leaves rustle; wind vane moved by wind

3

Gentle breeze

3,4 - 5,4

12 - 19

Leaves and small twigs in constant motion; light flags extended

4

Moderate breeze

5,5 - 7,9

20 - 28

Raises dust and loose paper; small branches moved

5

Fresh breeze

8,0 - 10,7

29 - 38

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

6

Strong breeze

10,8 - 13,8

39 - 49

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

7

High wind,
moderate gale,
near gale

13,9 - 17,1

50 - 61

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

8

Gale,
fresh gale

17,2 - 20,7

62 - 74

Twigs break off trees; generally impedes progress

9

Strong/severe gale

20,8 - 24,4

75 - 88

Slight structural damage (chimney pots and slates removed)

10

Storm,
whole gale

24,5 - 28,4

89 - 102

Seldom experienced inland; trees uprooted; considerable structural damage

11

Violent storm

28,5 - 32,6

103 - 117

Very rarely experienced; accompanied by widespread damage

12

Hurricane-force

ab 32,7

ab 118

Devastation