My source came from watching some documentary of battles pre-gunpowder, it was probably the commentator elaborating for dramatic effect. Let me put this to F.L.A.S.K: St Swithin or Swithun was Bishop of Winchester and he died in AD 862 He was adopted as the patron saint of Winchester and in the 12th century the doggerel lines were penned. "St Swithin's day if thou dost rain For forty days it will remain St Swithin's day if thou be fair For forty days will rain na mair" Bishop of Winchester 852-862 although very little is known about him other than from legends. In 971 Bishop Ethelwold moved Swithun's remains to a new shrine, commissioned by King Edgar, to Winchester Cathedral (the Old Minster not the present one) which became a place of pilgrimage as miracles were worked at the tomb. In the 990's Swithun's sanctity and miracles were celebrated by two Winchester writers as well as in Aelfric's "Lives of the Saints". His cult continues to flourish in the Middle Ages. His day is 15th July; if it rains then it will rain for 40 days because Swithun, a humble man, wished to be buried in the graveyard at Winchester and not in a fine tomb, cursing the land with 40 days of rain should the latter be done. And tomorrow is the 15th July.