There was a recent thread on this very subject a week or two ago but can't find it at the moment. The plant under discussion then was a lilac I believe but this can happen to a number of trees and shrubs......flowering out of season.

The consensus is that a stressful climate event disrupts the plant's biological systems and 'tricks' it into thinking it should be flowering. The event could be drought, drought followed by plentiful rainfall, abrupt temperature changes, etc.

Any fruit that might be involved is unlikely to happen and the erratic flowering may or may not reduce or delay the regular flowering in the coming season. The vote is still out on that as some species seem to be totally unaffected by this issue.