Estimating Wind Speed - National Weather Service

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Estimating Wind Speed

[ Also, see estimating wind speed and sea states while at sea ]

Estimating Wind Speeds with Visual Clues [ printable version .pdf ]
Beaufort number Description Speed Visual Clues and Damage Effects
0 Calm Calm Calm wind. Smoke rises vertically with little if any drift.
1 Light Air 1 to 3 mph Direction of wind shown by smoke drift, not by wind vanes. Little if any movement with flags. Wind barely moves tree leaves.
2 Light Breeze 4 to 7 mph Wind felt on face. Leaves rustle and small twigs move. Ordinary wind vanes move.
3 Gentle Breeze 8 to 12 mph Leaves and small twigs in constant motion. Wind blows up dry leaves from the ground. Flags are extended out.
4 Moderate Breeze 13 to 18 mph Wind moves small branches. Wind raises dust and loose paper from the ground and drives them along.
5 Fresh Breeze 19 to 24 mph Large branches and small trees in leaf begin to sway. Crested wavelets form on inland lakes and large rivers.
6 Strong Breeze 25 to 31 mph Large branches in continuous motion. Whistling sounds heard in overhead or nearby power and telephone lines. Umbrellas used with difficulty.
7 Near Gale 32 to 38 mph Whole trees in motion. Inconvenience felt when walking against the wind.
8 Gale 39 to 46 mph Wind breaks twigs and small branches. Wind generally impedes walking.
9 Strong Gale 47 to 54 mph Structural damage occurs, such as chimney covers, roofing tiles blown off, and television antennas damaged. Ground is littered with many small twigs and broken branches.
10 Whole Gale 55 to 63 mph Considerable structural damage occurs, especially on roofs. Small trees may be blown over and uprooted.
11 Storm Force 64 to 75 mph Widespread damage occurs. Larger trees blown over and uprooted.
12 Hurricane Force over 75 mph Severe and extensive damage. Roofs can be peeled off. Windows broken. Trees uprooted. RVs and small mobile homes overturned. Moving automobiles can be pushed off the roadways.

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