Has anybody else been reading this thread with a puzzled frown, wondering whether it isn't supposed to be 'Swithin'?

Well, here's the answer:

Saint Swithun or Swithin (Old English: Swīþhūn; died c. 862) was an Anglo-Saxon bishop of Winchester and subsequently patron saint of Winchester Cathedral. His historical importance as bishop is overshadowed by his reputation for posthumous miracle-working. According to tradition, the weather on his feast day (15 July) will continue for forty days.

Now I wonder if the spelling 'Swīþhūn' means that his name had a long U and was originally pronounced Swith-OON, like Sas-SOON. It seems to me that someone named Swith-OON would have more mastery over clouds than a mere SWITHin.