Like most in the United Kingdom, I have been trapped in my house by snow for most of the last week. Waking up again like Bill Murray in Groundhog Day, to another snowy view, I have been dreaming of summer days to come. It was against this background that I thought I would get around to testing whether an old British weather proverb was true: St. Swithun's day if thou dost rain For forty days it will remain St. Swithun's day if thou be fair For forty days 'twill rain no more