Technically late May is still spring. I shall have to notify him of this, when betadom begins.

Astronomically Summer starts in June, but I've always referred to Summer as starting at the end of May, at least in the UK everyone I know follows that rule, we're british so we need all the summer we can get. I wouldn't be surprised if it was the same in the US, usually there's a holiday that goes with it like Memorial Day.