The Beaufort wind scale
Force
(Beaufort)
Knots
m/s
km/h
Pressure
in N/m²
Description
0
0-1
00,2
>1
0
Calm
1
1-3
0,3 1,5
1-5
0-1
Light Air
Ripples with the appearance of scales are
formed, but without foam crests.
Smoke drifts slowly.
2
4-6
1,6 3,3
6 - 11
2-6
Light Breeze
Small wavelets, crests glassy, no breaking
Wind felt on face, leaves rustle, vanes
begin to move
3
7 - 10
3,4 5,4
12 19
7 - 18
Gentle
Breeze
Large wavelets, crests begin to break,
scattered whitecaps
Leaves and small twigs constantly moving,
light flags extended
4
11 16
5,5 7,9
20 28
19 - 38
Moderate
Breeze
Small waves 1-4 ft. becoming longer,
numerous whitecaps
Dust, leaves, and loose paper lifted, small
tree branches move
5
17 21
8,0 10,7
29 38
39 - 71
Fresh Breeze
Moderate waves 4-8 ft taking longer form,
many whitecaps, some spray
Small trees in leaf begin to sway
6
22 27
10,8 13,8
39 49
72 - 117
Strong
Breeze
Larger waves 8-13 ft, whitecaps common,
more spray
Larger tree branches moving, whistling in
wires
7
28 33
13,9 17,1
50 61
Near Gale
Sea heaps up, waves 13-20 ft, white foam
streaks off breakers
Whole trees moving, resistance felt
walking against wind
Gale
Moderately high (13-20 ft) waves of
greater length, edges of crests begin to
break into spindrift, foam blown in streaks
Whole trees in motion, resistance felt
walking against wind
8
9
34 40
41 47
17,2 20,7
20,8 24,4
62 74
75 88
10
48 55
24,5 28,4
89 102
11
56 63
28,5 32,6
103 117
118 - 179
180 - 263
264 - 366
Strong Gale
Specifications for use at sea
and on land
Sea like a mirror.
Smoke rises vertically.
High waves (20 ft), sea begins to roll,
dense streaks of foam, spray may reduce
visibility
Slight structural damage occurs, slate
blows off roofs
367 - 495
Storm
Very high waves (20-30 ft) with
overhanging crests, sea white with densely
blown foam, heavy rolling, lowered
visibility
Seldom experienced on land, trees broken
or uprooted, "considerable structural
damage"
496 - 652
Violent
Storm
Exceptionally high (30-45 ft) waves, foam
patches cover sea,
visibility more reduced
Disrooted trees
12
64 72
32,7 36,9
118 134
653 - 830
Hurricane
Air filled with foam, waves over 45 ft, sea
completely white with driving spray,
visibility greatly reduced
Desolated houses and woods
13 -17
73 109
37 56
134 202
835 1913
Hurricane
Occurance only on ocean and seaside