Channel Swimming & Piloting Federation "Nothing great is easy", Captain Matthew Webb

Beaufort Scale 

0Calm1Sea like a mirrorCalm. Smoke rises vertically.
1Light Air1-3Ripples with the appearance of scales are formed, but without foam crestsWind motion visible in smoke.
2Light Breeze4-6Small wavelets, still short, but more pronounced. Crests have a glassy appearance and do not breakWind felt on exposed skin. Leaves rustle.
3Gentle Breeze7-10Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered white horsesLeaves and smaller twigs in constant motion.
4Moderate Breeze10-15Small waves, becoming larger; fairly frequent white horsesDust and loose paper raised. Small branches begin to move.
5Fresh Breeze16-21Moderate waves, taking a more pronounced long form; many white horses are formed. Chance of some sprayBranches of a moderate size move. Small trees begin to sway.
6Strong breeze22-27Large waves begin to form; the white foam crests are more extensive everywhere. Probably some sprayLarge branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over.
7High wind, near gale28-33Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the windWhole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors.
8Gale34-40Moderately high waves of greater length; edges of crests begin to break into spindrift. The foam is blown in well-marked streaks along the direction of the windTwigs broken from trees. Cars veer on road.
9Severe Gale41-47High waves. Dense streaks of foam along the direction of the wind. Crests of waves begin to topple, tumble and roll over. Spray may affect visibilityLarger branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies.
10Storm48-55Very high waves with long over-hanging 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 on a white appearance. The 'tumbling' of the sea becomes heavy and shock-like. Visibility affectedTrees are broken off or uprooted, saplings bent and deformed, poorly attached asphalt shingles and shingles in poor condition peel off roofs.
11Violent Storm56-63Exceptionally high waves (small and medium-size ships might disappear behind the waves). The sea is completely covered with long white patches of foam flying along the direction of the wind. Everywhere the edges of the wave crests are blown into froth. Visibility affectedWidespread vegetation damage. More damage to most roofing surfaces, asphalt tiles that have curled up and/or fractured due to age may break away completely.
12Hurricane64-71The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affectedConsiderable and widespread damage to vegetation, a few windows broken, structural damage to mobile homes and poorly constructed sheds and barns. Debris may be hurled about.