Antonin -- I agree with all of the above advice, and would definitely throw something over your cherry tree if you can; it may be okay without it, but why take a chance? I lost almost all of the flowers on a rhododendron bush one year because I figured if it was hardy enough to grow here it would be okay...
And for the southerners that have offered to send some warm air to Detroit -- send enough to share with the UP, please!!