I agree with anthropic that the greatest risk is rain following application. Keep in mind that the orchard is producing food and so the chemicals used necessarily degrade rapidly so as to be at acceptable concentrations for consumption by human when marketed. The orchard keeper doesn't want to waste chemical treatments by losing the application to rain and so this consideration will affect timing of applications based on weather forecasts. The timing of applications in fair weather should reduce any risks you may face.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers