Sunburn is the term used to describe the burns and blisters that can be caused by the exposure of a vampire's skin to sunlight.
Despite the fact that a vampire's skin was made to stand the test of time, and ceases to age when a vampire has crossed over into Darkness, it is very susceptible to sunlight, and any exposure to the Sun's UV rays causes a vampire's flesh to painfully blister, split, and burn, on contact. A minute or two in the sun will cause nausea, fever, and severe disorientation. After that, the skin begins to burn and peel, leaving a dark blackened scar wherever the Sun's rays hit. These damaging burns do not heal, even with the healing Sleep Cycles of a vampire's daily hibernation. Further extended exposure to sunlight leads the vampire to burst into flames and turns the flesh and bone to pure ash; death is instantaneous.
While 'death by sunlight' is a very painful way to die, many vampires who have reached the 'end of their life' will go on a Sun Quest and purposefully await the rising of the Sun, in order to see the Sun one more time.