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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