Ne'er cast a clout till May is out
One of the suggested derivations for this is that it doesn't refer to the month, but to the May tree, more widely known as Hawthorn. This traditionally blossoms near the end of May, so even if you did misunderstand the meaning of the saying, the timing was much the same*.
Not this year. It's out already.
*The next trick is to know what a clout is, and how to cast one. The OED suggest among other things that "clout" is "Applied contemptuously to any article of clothing". People generally interpret the saying as meaning winter clothing, such as vests.