When are roads most slippery during rain?

The time just after it begins to rain is considered the most slippery period on the road. This phenomenon occurs because the initial rain mixes with the accumulated oils and dirt on the roadway, creating a slick surface. These substances can form a layer that significantly reduces traction for vehicles, making it particularly hazardous during this early phase of rainfall.

As the rain continues, the water can help to wash away these contaminants, improving conditions somewhat. However, the first rain tends to lift the oils to the surface, and drivers are often not prepared for the sudden decrease in grip. Understanding this timing can aid drivers in taking extra precautions, such as reducing speed and increasing following distances, during these first moments of light rain.