How does humidity affect the likelihood of vapor drift?

Low humidity levels increase the likelihood of vapor drift because when the air is dry, herbicides can evaporate more readily. This evaporation results in the formation of small aerosol droplets that can be carried off by the wind, causing potential drift to unintended areas. When humidity is low, the ambient moisture in the air is insufficient to help retain the herbicide particles on the target surface, resulting in increased risks of vaporization and subsequent drift.

High humidity, on the other hand, tends to keep more moisture in the air, which can help reduce evaporation and keep the herbicide particles closer to the ground or on the intended crop. This is why it’s essential for applicators to monitor local humidity levels before conducting treatments, as low humidity conditions can significantly impact the effectiveness and safety of herbicide application.