Maybe you had a killing frost? It was a rough spring for frosts.

Scott

I am guessing but our very warm winter may created a negative chill hour effect during the hot days.

That could account for this year, but not years in a row of the same pattern in a bearing-age tree.

I had the same thing happen on a similarly aged Montmorecy tree a couple of years ago. I don't really know the cause. I don't think it was frost, since my North Star cherry and other fruit trees did just fine. Nor was it lack of pollination, since I have three hives of honey bees and a large population of orchard bees. Two hypotheses come to mind: (1) a heavy crop the previous year led to a very light crop the following year; (2) the tree needs pruning to encourage a larger crop. I have only minimally pruned my Montmorency cherry. To be honest, I don't really have a good grasp on how to prune a cherry tree. Any suggestions would be greatly welcomed.

well, I did prune it before it bloomed (I always prune it and use the same guidelines every year, nothing different this year); it did bloom plenty of flowers; I saw a decent amount of bees and other bugs flying around it; it has a very healthy green top with new growth; but only ONE FRUIT?

http://www.centuryfarmorchards.com/video/prunedemo.htm
This is a good demo on pruning apple tree - but it helps get an idea for any orchard tree;

You can probably search Youtube for video demo -- people post good stuff there