Motorists encountering a rainstorm should be aware that the roadway can be slick and that the worst time to drive is:

The correct answer emphasizes the specific dangers that are present at the beginning of a rainstorm. When rainfall first begins, it tends to mix with dust, oil, and debris that have accumulated on the roadway, creating a particularly slippery surface. This combination can lead to reduced traction and an increased risk of losing control of the vehicle. It is during this initial period that the roads are most hazardous, as the water has not yet had time to wash away these materials.

As the storm continues, the rain often helps to clear some of the oil and debris off the road, potentially making it safer compared to the onset of the rain. Additionally, during heavy rain, drivers may become more cautious and slow down, which can help mitigate risk. While driving after the rain stops may still present some hazards, such as standing water or reduced visibility due to just-fallen debris, these are generally less immediately dangerous than the conditions found at the storm's outset. Understanding this concept is crucial for safe driving practices in adverse weather conditions.