This scale gauges wind speed through the use of observations of the winds effects on trees and other objects. It is often used in monitoring projects because it is simple to understand and does not require specialized equipment.
Example: A “light breeze” is recorded as “2B” in the appropriate section of the spray diary.
| B. No | Approx speed | Classification and Description | |
| 0 | > 2 km/h | Calm | Still, smoke will rise vertically. |
| 1 | 2 – 5 km/h | Light Air | Rising smoke drifts, weather vane is inactive. |
| 2 | 5 – 12 km/h | Light Breeze | Leaves rustle, can feel wind on your face, weather vane is active. |
| 3 | 12 – 20 km/h | Gentle Breeze | Leaves and twigs move around. Light weight flags extend. |
| 4 | 20 – 30 km/h | Moderate Breeze | Thin branches move around, raises dust and paper. |
| 5 | 30 – 40 km/h | Fresh Breeze | Trees move and sway. |