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 |
| Advisory-force | 6 | 25–31 mph
(40–50 km/h) | Large branches in motion; whistling in telephone wires. |
| Advisory-force | 7 | 32–38 mph
(51–62 km/h) | Whole trees in motion; inconvenience felt walking against wind. |
| Gale-force | 8–9 | 39–54 mph
(63–88 km/h) | Twigs break off trees; wind generally impedes progress. Tropical storm criteria begin. |
| Storm-force | 10–11 | 55–73 mph
(89–117 km/h) | Damage to chimneys and television antennas; pushes over shallow-rooted trees. Severe thunderstorm criteria begin (58 mph (93 km/h)). |
| Hurricane-force | 12–13† | 74–112 mph
(118–181 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. |
Major hurricane-force
Extreme wind | 14–16† | 113–237 mph
(182–381 km/h) | 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.