Which weather factor most directly affects spray drift?

• A. Temperature and humidity.
• B. Cloud cover.
• C. Wind speed.
• D. Wind speed and humidity.

Answer: (D)

Spray drift is driven most directly by how droplets behave once they leave the nozzle. Wind speed pushes droplets away from the target, so stronger winds carry droplets farther before they settle. Humidity affects evaporation: in drier air, droplets evaporate quickly and become smaller and lighter, which makes them more easily carried aloft by the breeze and travel farther. In more humid air, evaporation slows, droplets stay larger and heavier, so they’re more likely to deposit closer to the target. Because drift depends on both how far droplets travel and how they shrink in air, the combination of wind speed and humidity best explains spray drift.