| Force | Description | Commonly Observable Phenomena | Wind speed Km/h | Wind speed Knots |
| 0 | Calm | Smoke rises vertically | 0-1 | <1 |
| 1 | Light air | Wind direction indicated by smoke but not wind vanes | 1-5 | 1-3 |
| 2 | Light breeze | Wind noticeable, leaves move, wind vane moves. | 6-11 | 4-6 |
| 3 | Gentle breeze | Leaves and small twigs in constant motion. | 12-19 | 7-10 |
| 4 | Moderate breeze | Wind raises dust and loose paper. Small branches are moved. | 20-29 | 11-16 |
| 5 | Fresh breeze | Small trees in leaf start to sway.Crested wavelets form on inland waters. | 30-39 | 17-21 |
| 6 | Strong breeze | Large branches in motion, wind whistles. Umbrellas used with difficulty. | 40-50 | 22-27 |
| 7 | Near gale. | Trees in motion, awkward to walk against wind. | 51-61 | 28-33 |
| 8 | Gale | Twigs break, hard to walk. | 62-74 | 34-40 |
| 9 | Strong gale | Some structural damage may occur, slates removed etc. | 75-87 | 41-47 |
| 10 | Storm | Trees uprooted, considerable structural damage. | 88-101 | 48-55 |
| 11 | Violent storm | Widespread damage. | 102-117 | 56-63 |
| 12 | Hurricane | Widespread damage. | 118+ | >63 |
