The RSA recommends you allow a minimum overall stopping distance of (see table below):
Skidding
Any factor which reduces the grip of your tyres on the road is a possible source of skidding. Wet or greasy roads, overloading, worn or improperly inflated tyres, mud, leaves, ice, snow, harsh acceleration, sudden braking, or excessive speed for the conditions can all cause or contribute to a skid.
‘Aquaplaning’ occurs when a car is being driven on a wet road and a film of water builds up between the tyres and the road surface.
When that happens, the car loses contact with the road, and braking and steering are affected.