| Scale | Force Rating | Observable Land Effects | Speed MPH | Effect at sea |
| 0 | Calm | Vertical Smoke | 1 | Calm (Glassy) |
| 1 | Light Air | Slight smoke drift | 1-3 | Calm (Rippled) |
| 2 | Light Breeze | Leaves gently rustle | 4-7 | Smooth (wavelets) |
| 3 | Gentle Breeze | Leaves and twigs move | 8-12 | Slight |
| 4 | Moderate Breeze | Raises paper moves small branches | 13-18 | Slight to Moderate |
| 5 | Fresh Breeze | Sways small leafy trees | 19-24 | Moderate |
| 6 | Strong Breeze | Sways large branches | 25-31 | Rough |
| 7 | Moderate Gale | Trees sway | 32-38 | Rough to very rough |
| 8 | Fresh Gale | Broken twigs, walking impeded | 39-46 | Very rough to high |
| 9 | Strong Gale | Chimneys, slates, hoardings damaged | 47-54 | High |
| 10 | Whole Gale | Trees Blown Down and Considerable damage | 55-63 | Very high |
| 11 | Storm | Major Damage | 64-75 | Very high |
| 12 | Hurricane | Very dangerous tropical whirling winds | 76+ | Phenomenal |