The RHS has reported that we could be facing a fruitless summer this year, as the winter chill, supposedly required for various fruits to crop, has been mostly absent. Bushes are also flowering early. While frost might be a real problem in killing off early blossom, the high winter temperatures aren't necessarily a cause for despair. It seems that we probably don't know as much about the temperature requirements, certainly of apple trees, as we think.
For an alternative view, do see my post from last November, A Chilling Time for Apples Ahead? Or go straight to the Apples and Oranges blog for an eye-opener on parts of the world that grow apples where convention says it's impossible.