If you are driving on a highway in heavy rain, you must slow down your vehicle to avoid:

When driving on a highway in heavy rain, slowing down is crucial to avoid hydroplaning. Hydroplaning occurs when a layer of water builds up between the tires of the vehicle and the road, causing the tires to lose contact with the surface. This results in a loss of control over the vehicle as it can no longer grip the road properly. By reducing your speed, you decrease the chances of the tires encountering enough water to lose traction, allowing for better control and responsiveness.

While skidding can also occur in wet conditions, especially if one were to brake suddenly or turn too sharply, reducing speed primarily helps manage the risk of hydroplaning first and foremost. Losing visibility and overheating brakes also pose risks when driving in heavy rain, but the immediate concern when it comes to speed is preventing hydroplaning, which is a direct consequence of driving too fast on wet surfaces.