| Index | Definition | Observation | km/h | mph
|
| 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
|
