Ours are in bloom now, and will continue through September. These small trees will survive up through Zone 6, but in Zone 6 they prefer some shelter from the winter winds, and they are slow to emerge from dormancy (they look dead).
They are common in the South, but up here people are stunned by such a brilliantly summer-blooming tree and don't know what it is.
They like to be pruned properly, and heavily mulched, and need full sun to produce those blooms. A little fertilizer, too.
This is a young plant, with three main stems. I much prefer them with multiple stems rather than with a single trunk.
The exfoliating bark is interesting too.
51 varieties here, with photos. Most of our cultivars are of Asian descent, but there are native species. More photos, and how to grow them, here.
Growing plants on or above their zonal limits is always an interesting challenge for us gardeners. A fully-rational person would not bother.