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Beaufort Wind Scales for Land.

  

Beaufort Wind Scales for Sea. 

 

 

Beaufort Weather Notation.

 

Windchill Equivalent Temperature.

 

Beaufort Wind Scale (Land)

Beaufort 

Number 

Wind 

Effect on land 

Speed 

(Knots) 

Speed 

(mph) 

0 

Calm 

Smoke Rises Vertically 

Less than 1 

Less than 

1 

1 

Light Air 

Direction shown by smoke but not wind vanes 

1-3 

1-3 

2 

Light breeze 

Wind felt on face; leaves rustle; wind vanes 

move. 

4-6 

4-7 

3 

Gentle 

breeze 

Leaves & twigs in motion; wind extends light 

flag 

7-10 

8-12 

4 

Moderate 

breeze 

Raises dust & loose paper; moves small 

branches. 

11-16 

13-18 

5 

Fresh breeze

Small trees in leaf begin to sway. 

17-21 

19-24 

6 

Strong 
breeze 

Large branches in motion; whistling in 

telegraph wires; difficulty with umbrellas. 

22-27 

25-31 

7 

Moderate 

gale 

Whole trees in motion; difficult to walk against 

wind. 

28-33 

32-38 

8 

Fresh gale 

Twigs break off trees; progress impeded. 

34-40 

39-46 

9 

Strong gale 

Slight structural damage occurs; chimney pots 

& slates blown off. 

41-47 

47-54 

10 

Whole gale 

Trees uprooted and considerable structural 

damage. 

48-56 

55-63 

11 

Storm 

Widespread damage; seldom experienced in 

UK. 

57-65 

64-75 

12 

Hurricane 

Winds of this force rarely encountered outside 

tropical revolving storms. 

Over 65 

Over 75 

 

Beaufort Wind Scale (Sea)

Beaufort 

Number 

Wind 

Effect on land 

Speed 

(Knots) 

Wave 

Height 

(m) 

0 

Calm 

Sea like a mirror. 

Less than 

1 

0 

1 

Light Air 

Ripples formed but without foam crests. 

1-3 

0.1 

2 

Light 

breeze 

Small wavelets; crests have glassy appearance but 

do not break. 

4-6 

0.2 

3 

Gentle 

breeze 

Large wavelets. Crests begin to break. Perhaps 

scattered white horses. 

7-10 

0.6 

4 

Moderate 

breeze 

Small waves becoming longer; fairly frequent white 

horses. 

11-16 

1.0 

5 

Fresh 

breeze 

Moderate waves, taking more pronounced long form; 

many white horses. 

17-21 

2.0 

6 

Strong 
breeze 

Large waves begin to form; the foam crests are more

extensive everywhere. (Probably some spray.) 

22-27 

3.0 

7 

Moderate 

gale 

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

wind. 

28-33 

4.0 

8 

Fresh gale 

Moderately high waves of greater length; The foam is

blown into well marked streaks along direction of 

wind. 

34-40 

5.5 

9 

Strong 

gale 

High waves. Crests begin to topple, tumble and roll 

over. Spray may affect visibility. 

41-47 

7.0 

10 

Whole gale

Very high waves with long overhanging crests. The 

sea takes on a white appearance. Visibility affected. 

48-56 

9.0 

11 

Storm 

Exceptionally high waves. (Small & medium sized 

ships may be lost to view behind waves.) Everywhere

the edges of wave crests are blown into froth. 

Visibility affected. 

57-65 

11.5 

12 

Hurricane 

The air is filled with foam & spray. Sea completely 

white with driving spray; visibility seriously affected. 

Over 65 

>14 

 

Beaufort Weather Notation

Weather

Beaufort 
Notation

Weather

Beaufort 
Notation

Blue Sky (0-2/8 cloud)

b

Snow

s

Overcast (Whole sky covered with 
Unbroken cloud)

o

Fog

f

Partly Clouded (3/8 to 5/8 cloud)

bc

Thunder

t

Squally weather

q

Gale

g

Cloudy (6/8 to 8/8 cloud)

c

Thunderstorm with rain 
or snow

tlr or tls

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Rain

r

Hail

h

Drizzle

d

Precipitation in sight

jp

Sleet

rs

Ugly threatening sky

u

Wet Air (no Precipitation)

e

Dust Haze

z

Unusual Visibility

v

Hoar Frost

x

Line squall

kq

Lightning

l

Dew

w

Dry air

y

Storm of drifting Snow

ks

Mist

m

 

Windchill Equivalent Temperature.

Beaufort 

Force

Wind Speed 
at 10 metre 

height

Air Temperature °C

 

Knots

ms-1

-40

-35 -30 -25 -20 -15 -10

-5

0

5

10

15 

1

2

0.8

-41

-36 -31 -26 -21 -15 -10

-5

0

+5

+10 +15

2

5

2.4

-43

-38 -32 -27 -22 -17 -12

-7

-1

+4

+9 +14

3

8.5

4.3

-47

-42 -37 -31 -26 -20 -15

-9

-4

+2

+7 +13

4

13.5

6.7

-52

-47 -41 -35 -30 -24 -18 -12

-7

-1

+5 +11

5

19

9.3

-57

-51 -45 -39 -33 -27 -21 -15

-9

-3

+3

+9

6

24.5

12.3

-61

-55 -49 -43 -37 -31 -24 -18 -11

-5

+2

+8

7

30.5

15.5

-65

-59 -52 -46 -40 -33 -27 -20 -13

-6

+0

+7

8

37

18.9

-68

-62 -55 -49 -42 -36 -29 -22 -15

-8

-1

+6

9

44

22.6

-72

-64 -59 -52 -45 -38 -31 -24 -17 -10

-2

+5

 

 

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"Windchill" is a term normally used to express the combined effect of low air temperature and of 
wind on a standing or walking human. It can be measured by the rate of heat loss per unit area, 

the "windchill factor" or more commonly by the "windchill equivalent temperature" (WET). No 

allowance is made for precipitation or sea spray. Windchill does not apply to inanimate objects, 

even heat producing engines. In "full" sunshine, a correction of about +7°C at low wind speeds and 

+3°C at gale force should be made.  

The concept is useful in countries which experience cold winters to distinguish the difference in 

human comfort and risk of exposure between light and strong winds.

::Copyright J. Cranston:: 

2000 - 2006 

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