The Beaufort Scale

In 1805 Admiral Francis Beaufort developed a scale based on wind speed to estimate the effect of wind on the environment and things around us, such as water, trees, buildings, etc. The first scale estimated the effects of wind on the ocean. Later, a separate scale was designed for wind effects on land. This scale is given below.

Beaufort Number	Wind Speed (MPH)	Weather Forecast Terms	Wind's Effects on the Land Environment
0	Under 1	Calm	Calm smoke rises vertically; no leaf motion
1	1-3	Light	Smoke drift shows wind direction; wind vanes don't respond
2	4-7	Light	Wind felt on face; leaves start rustling; wind vanes respond
3	8-12	Breezy	Leaves, small twigs in constant motion; light flags extended
4	13-18	Breezy	Dust, leaves, loose paper and other litter is raised; small branches move
5	19-24	Breezy	Small trees in leaf begin to sway
6	25-31	Windy	Large tree branches in motion; whistling heard in overhead wires
7	32-38	Strong winds; very windy	Whole trees in motion, resistance felt when walking against the wind
8	39-46	High winds; high wind warning	Twigs and small branches broken off trees
9	47-54	High winds; high wind warning	Slight structural damage occurs, slate blown off roofs, wires may snap
10	55-63	Severe thunderstorm	Structural damage; trees broken
11	64-73	Severe wind	Widespread damage
12	>73	Hurricane force	Violence and destruction; flying debris from objects destroyed earlier damages additional structures

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