Storm Warning Flags
Small Craft Warning 21-38 mph (18-33 kts)	Gale Warning 39-54 mph (34-47 kts)	Storm Warning 55-73 mph (48-63 kts)	Hurricane Warning 74+ mph (64+ kts)

The Beaufort Scale, devised in 1805 by Sir Francis Beaufort (1774-1875), is a system for estimating wind strengths without the use of instruments, based on the effects wind has on the physical environment. The behavior of smoke, waves, trees, etc., is rated on a 13 point scale of 0 to 12.

Beaufort Scale
FORCE	DESC	MPH	EFFECTS
0	Calm	0-1	Smoke rises vertically
1	Light Air	1-3	Rising smoke drifts
2	Light Breeze	4-7	Leaves rustle
3	Gentle Breeze	8-12	Light flags extend
4	Moderate Breeze	13-18	Moves thin branches
5	Fresh Breeze	19-24	Small trees sway
6	Strong Breeze	25-31	Large tree branches move
7	Moderate Gale	32-38	Large trees begin to sway
8	Fresh Gale	39-46	Small branches are broken from trees
9	Strong Gale	47-54	Slight damage occurs to buildings
10	Whole Gale	55-63	Large trees uprooted, building damage
11	Storm	64-74	Extensive widespread damage
12	Hurricane	74+	Extreme destruction

 The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Herbert Saffir, an engineer in Coral Gables, Fla., and Robert Simpson, who was then director of the National Hurricane Center, developed the scale in the early 1970s.