| Force |
Name |
Wind Speed
knots mph |
Consequence |
| 0 |
Calm |
0 |
0 |
Smoke rises vertically |
|
Wave height: 0 m - Sea:
Like a mirror |
| 1 |
Light air |
1-3 |
1-3 |
Smoke drifts with air
|
|
Wave height: 0.1 m
(.25 ft) - Sea: Ripples - No foam crests |
| 2 |
Light breeze |
4-6 |
4-7 |
Weather vanes become active |
|
Wave height: 0.2-0.3
m (0.5-1 ft) - Sea: Small wavelets - Not breaking |
| 3 |
Gentle breeze |
7-10 |
8-12 |
Leaves and small twigs move |
|
Wave height: 0.6-1 m
(2-3 ft) - Sea: Small wavelets - Crests begin to break |
| 4 |
Moderate breeze |
11-16 |
13-18 |
Small branches sway |
|
Wave height: 1-1.5 m
- Sea: Small waves becoming longer, numerous whitecaps. |
| 5 |
Fresh breeze |
17-21 |
19-24 |
Small trees sway - Waves
break |
|
Wave height: 2-2.5 m
(6-8 ft) - Sea: Moderate waves - Many whitecaps |
| 6 |
Strong breeze |
22-27 |
25-31 |
Large branches sway |
|
Wave height: 3-4 m
(9.5-13 ft) - Sea: Larger waves forming - Whitecaps everywhere |
| 7 |
Near gale |
28-33 |
32-38 |
Whole trees sway -
difficult to walk |
|
Wave height: 4-5.5 m
(13.5-19 ft) - Sea: Sea heaps up - White foam blown around |
| 8 |
Gale |
34-40 |
39-46 |
Twigs break off trees |
|
Wave height: 5.5-7.5
m (18-25 ft) - Sea: Edges of crests break into spindrifts |
| 9 |
Strong gale |
41-47 |
47-54 |
Shingles blow off roofs |
|
Wave height: 7-10 m
(23-32 ft) - Sea: High waves - Sea rolls - Reduced visibility |
| 10 |
Storm |
48-55 |
55-63 |
Trees uprooted - Damage to
buildings |
|
Wave height: 9-12.5 m
(29-41 ft) - Sea: Very high waves with overhanging crests |
| 11 |
Violent
Storm |
56-63 |
64-73 |
Widespread damage |
|
Wave height: 11.5-16
m (37-52 ft) - Sea: Exceptionally high waves |
| 12 |
Hurricane |
Over 63 |
Over 73 |
Violent destruction |
|
Wave height: 16+ m
(52+ ft) - Sea: Sea completely white - Excessive foam |
weather.gov 
