Wind Speed
Wind speed and direction must be taken into account before you start spraying. You need to ask yourself:
- How fast is the wind blowing?
- Is the wind blowing towards or away from sensitive areas?
You can measure wind speed with a hand-held anenometer. These are available from outdoor and boating retailers from between $75 - $250. Make sure you get a model that operates well at low wind speeds.
Alternatively, use the benchmarks in the following table to assess wind speed.
| Wind speed guide |
| Approx. airspeed at nozzle height |
Description |
Visible signs |
Spraying |
| Less than 2 km/h |
Calm |
Smoke rises vertically |
Use only medium or coarse spray quality |
| 2 - 3 km/h |
Light air |
Direction shown by smoke drift |
Avoid fine spray on warm, sunny days |
| 3 - 6 km/h |
Light breeze |
Leaves rustle, wind felt on face |
Ideal spraying conditions |
| 6 - 10 km/h |
Gentle breeze |
Leaves and twigs in constant motion |
Good spraying |
| 10 - 15 km/h |
Moderate breeze |
Small branches move, raises dust or loose paper |
Increased risk of spray drift, avoid fine sprays |
| 15-20 km/h |
Fresh breeze |
Small trees sway |
Extreme caution with any sprays |
| >20 km/h |
Strong breeze |
Large branches sway |
Unsuitable for spraying |
|