| Beau- fort No | Description | Cyclone category | Average wind speed (Knots) | Average wind speed (kilometres per hour) | Specifications for estimating speed over land | Specifications for estimating speed over water |
| 0 | Calm | | Less than 1 | less than 1 | Calm, smoke rises vertically. | Sea like mirror |
| 1 | Light Air | | 01-Mar | 01-May | Direction of wind shown by
smoke drift, but not by wind vanes. | Ripples with the appearance of scales are formed,
but without foam crests |
| 2 | Light breeze | | 04-Jun | 06-Nov | Wind felt on face; leaves rustle;
ordinary wind vane moved by wind. | Small wavelets, still short,
but more pronounced;
crests have a glassy ppearance and do not break |
| 3 | Gentle breeze | | 07-Oct | Dec-19 | Leaves and small twigs in constant motion;
wind extends light flag. | Large wavelets; crests begin to break;
foam of glassy appearance;
perhaps scattered white horses |
| 4 | Moderate breeze | | Nov-16 | 20 - 28 | Raises dust and loose paper;
small branches moved. | Small waves, becoming longer; fairly requent white horses |
| 5 | Fresh breeze | | 17 -21 | 29 - 38 | Small trees in leaf begin to sway;
crested wavelets form on inland waters. | Moderate waves,
taking a more pronounced long form; many white horses are formed
(chance of some spray) |
| 6 | Strong breeze | | 22 - 27 | 39 - 49 | Large branches in motion;
whistling heard in telegraph wires;
umbrellas used with difficulty. | Large waves begin to form; the white oam crests are more extensive everywhere (probably some spray) |
| 7 | Near gale | | 28 - 33 | 50 - 61 | Whole trees in motion;
inconvenience felt when
walking against the wind. | Sea heaps up and white foam from reaking waves begins to be blown in streaks along the direction of the wind |
| 8 | Gale | Category 1 | 34 - 40 | 62 - 74 | Breaks twigs off trees;
generally impedes progress. | Moderately high waves of greater length; edges of crests begin to break into the spindrift; the foam is blown in well marked streaks along the direction of the wind |
| 9 | Strong gale | Category 1 | 41 - 47 | 75 - 88 | Slight structural damage occurs
(chimney pots and slates removed). | High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble and roll over; spray may affect visibility |
| 10 | Storm | Category 2 | 48 - 55 | 89 - 102 | Seldom experienced inland;
trees uprooted;
considerable structural damage occurs. | Very high waves with long overhanging crests; the resulting foam, in great patches, is blown in dense white streaks along the direction of the wind; on the whole, the surface of the sea takes a white appearance; the tumbling of the sea becomes heavy and shock-like; visibility affected |
| 11 | Violent storm | Category 2 | 56 - 63 | 103 - 117 | Very rarely experienced;
accompanied by widespread damage. | Exceptionally high waves (small and medium sized ships might be for a time lost to view behind the waves); the sea is completely covered with long white patches of foam lying along the direction of the wind; everywhere the edges of the wave crests are blown into froth; isibility affected |
| 12 | Hurricane | Category 3,4,5 | 64 and over | 118 and over | Severe and extensive damage. | The air is filled with foam and spray; sea completely white with driving spray; visibility very seriously affected |
