Slow down and leave double the usual distance between you and the vehicle in front. Tyre grip is reduced on wet road surfaces and the car will travel farther before stopping when you brake.
In heavy rain, switch on your dipped headlights.
Take care when overtaking large vehicles, because the spray from their wheels can obscure your vision.
Take care on bends, even after a light shower. The moisture combined with the oil on the road surface can make roads very slippery.
Sensible advice