After a damp and chilly day coaching a client at Goodwood today I was emphasising the importance of adjusting your line to maximise your performance in different conditions.
Ignoring the intricacies of wet lines and going off line to find grip, a general rule of thumb is: the lower the grip level (e.g. wet) the more it gives you a surplus of power over grip. Therefore you need to turn in later and slower (carry less mid-corner speed) and make the exit straighter to allow you to get on the gas harder. With a straighter exit there is less lateral load on the tyre so you can use more gas to accelerate harder which will make you faster down the next straight.
In the dry you have more grip relative to your power so you turn in earlier to carry more mid-corner speed as you will have less acceleration potential on the exit.