| Beaufort number |
Description |
Wind speed |
Wave height |
Sea conditions |
Land conditions |
Sea state photo |
| km/h |
mph |
kts |
m/s |
m |
ft |
| 0 |
Calm |
< 1 |
< 1 |
< 1 |
< 0.3 |
0 |
0 |
Flat. |
Calm. Smoke rises vertically. |
 |
| 1 |
Light air |
1 – 5 |
1 – 3 |
1 – 2 |
0.3 – 1.5 |
0 – 0.2 |
0 – 1 |
Ripples without crests. |
Wind motion visible in smoke. |
 |
| 2 |
Light breeze |
6 – 11 |
3 – 7 |
3 – 6 |
1.5 – 3.3 |
0.2 – 0.5 |
1 – 2 |
Small wavelets. Crests of glassy appearance, not
breaking |
Wind felt on exposed skin. Leaves rustle. |
 |
| 3 |
Gentle breeze |
12 – 19 |
8 – 12 |
7 – 10 |
3.3 – 5.5 |
0.5 – 1 |
2 – 3.5 |
Large wavelets. Crests begin to break; scattered
whitecaps |
Leaves and smaller twigs in constant motion. |
 |
| 4 |
Moderate breeze |
20 – 28 |
13 – 17 |
11 – 15 |
5.5 – 8.0 |
1 – 2 |
3.5 – 6 |
Small waves with breaking crests. Fairly frequent
white horses. |
Dust and loose paper raised. Small branches begin
to move. |
 |
| 5 |
Fresh breeze |
29 – 38 |
18 – 24 |
16 – 20 |
8.0 – 11 |
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. |
 |
| 6 |
Strong breeze |
39 – 49 |
25 – 30 |
21 – 26 |
11 – 14 |
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
garbage cans tip over. |
 |
| 7 |
High wind, Moderate gale, Near gale |
50 – 61 |
31 – 38 |
27 – 33 |
14 – 17 |
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. |
 |
| 8 |
Gale, Fresh gale |
62 – 74 |
39 – 46 |
34 – 40 |
17 – 20 |
5.5 – 7.5 |
18 – 25 |
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. |
 |
| 9 |
Strong gale |
75 – 88 |
47 – 54 |
41 – 47 |
21 – 24 |
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. |
 |
| 10 |
Storm,
Whole gale |
89 – 102 |
55 – 63 |
48 – 55 |
25 – 28 |
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. |
 |
| 11 |
Violent storm |
103 – 117 |
64 – 72 |
56 – 63 |
29 – 32 |
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 vegetation damage. Many roofing surfaces
are damaged; asphalt tiles that have curled up and/or
fractured due to age may break away completely. |
 |
| 12 |
Hurricane |
= 118 |
= 73 |
= 64 |
= 33 |
= 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. |
 |
