The Beaufort scale is an empirical measure that correlates wind speed to observed conditions at sea or on land.
|Wind category||Beaufort number||Wind speed||Conditions|
|Large branches in motion; whistling in telephone wires.|
|Whole trees in motion; inconvenience felt walking against wind.|
|Twigs break off trees; wind generally impedes progress. Tropical storm criteria begin.|
|Damage to chimneys and television antennas; pushes over shallow-rooted trees. Severe thunderstorm criteria begin (58 mph (93 km/h)).|
|Peels shingles off roofs; windows broken if struck by debris; trees uprooted or snapped; mobile homes severely damaged or overturned; moving cars pushed off-road. Hurricane criteria begin.|
|Roofs torn off houses; cars lifted off ground; trees defoliated and sometimes debarked. Major hurricane criteria begin.|
†:Beaufort levels above 12 are non-standard in the United States. Instead, the Saffir–Simpson hurricane scale (Category 1, Category 2, etc.) is used.