Hydroplaning occurs when a vehicles tires lose contact with the actual road and instead ride on a layer of water. The vehicle can loose traction and have trouble steering, braking and accelerating. When this occurs do not panic! Also, do not brake or accelerate. If you do you most likely will spin out and lose control of the vehicle. Also sudden acceleration could pull the vehicle straight ahead which could be dangerous if the vehicle is pointed toward the edge of the roadway. Just take your foot off the gas to slow down. If you need to brake and you have No-ABS Brakes (anti-lock brakes), lightly pump the brakes until you slow down. Try and drive slow and steady until you can feel your tires grip the road again. Remember your tires have no contact with the road when hydroplaning, so if you start over-steering you could end up off the road.
Good tires are key to safe driving in the rain! Make sure to always check your tire tread routinely and check the air pressure as well. It could save your life! The water on the road needs to go somewhere and tires with good tread will channel the water under the tire so it can grip the road. Less Tread = more chance of hydroplaning.