St Swithun (or Swithin), was an Anglo-Saxon Bishop of Winchester, consecrated in 853AD. 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. The name of Swithun is best known today for a proverb, which says that if it rains on St Swithun’s Day, 15 July, it will rain for 40 days.
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 nae mare
Swithun, died around 862AD, was initially buried out of doors, rather than in his cathedral, apparently at his own request. William of Malmesbury recorded that the bishop left instructions that his body should be buried outside the church, “ubi et pedibus praetereuntium et stillicidiis ex alto rorantibus esset obnoxious” [where it might be subject to the feet of passers-by and to the raindrops pouring from on high], which has been taken as indicating that the legend was already well known in the 12th century.
In 971 it was decided to move his body to a new indoor shrine, and one theory traces the origin of the legend to a heavy shower by which, on the day of the move, the saint marked his displeasure towards those who were removing his remains. A much older tradition says that the move took place in accordance with the saint’s desire expressed in a vision. There is a scientific basis to the weather pattern behind the legend of St Swithun’s day. Around the middle of July, the jet stream settles into a pattern which, in the majority of years, holds reasonably steady until the end of August. When the jet stream lies north of the UK then continental high pressure is able to move in; when it lies across or south of the British Isles, Arctic air and Atlantic weather systems predominate. The most false that the prediction has been, were 1924 when 13.5 hours of sunshine in London were followed by 30 of the next 40 days being wet, and 1913 when a 15-hour rainstorm was followed by 30 dry days of 40.
Many ancient churches dedicated to St Swithun can be found throughout the south of England, especially in Hampshire. Strangely, devotion to him spread to Western Norway, where the cathedral at Stavanger is dedicated to him.
Fr Matthew (acknowledgments to Wikipedia!)