How can weather conditions before herbicide application affect the results?

Weather conditions preceding herbicide application are critical for ensuring optimal effectiveness. Rain or high winds can significantly influence the performance of herbicides. If there is rainfall shortly after application, the herbicide may wash off the target area, reducing its intended impact. Similarly, high winds can lead to drift, where the herbicide particles are carried away from the target plants, affecting both the efficacy and potentially harming neighboring crops or vegetation.

By contrast, other factors mentioned in the incorrect options do not accurately reflect the influence of weather on herbicide performance. For example, cold weather does not enhance a herbicide's strength; in fact, many herbicides are less effective in low temperatures because plant metabolism slows down. Additionally, while sunny conditions may improve some herbicides' effectiveness through increased absorption by plant leaves, they do not directly aid in soil penetration, which is more dependent on factors like soil moisture and texture. Thus, rain or high winds are the primary weather conditions that can directly compromise herbicide application outcomes.