Ne'er cast a clout till may be out

So is it do not remove any clothes until the month of May is finished or until the may blossom (hawthorn) has appeared? There are arguments for both etymologies but I prefer the latter as it seems very nesh to be still wrapped up at the end of May. That is, of course, in a normal month! I noticed the difference on my return from warmer climes and did not 'cast a clout' despite the blossom having been out for some time. My colleagues told me it is comparatively mild today but it did not feel so.

Apologies for the poor focus but the the branch was moving in the wind and until my birthday when I hope to get my better camera (hint, hint Mrs TT), I will have to continue to make excuses!