What is St Swithin's Day? Who was St Swithin, what's the saying about the weather on St Swithin's Day - is it a reliable forecasting system
St Swithin's Day takes place every year on 15 July - where does the legend come from?
According to traditional folklore, whatever the weather is like on St Swithin's Day - whether rain or sunshine - it will continue for the next 40 days and 40 nights. Swithin was a man born in or around the year 800. He became Bishop of Winchester.
Unlike other religious figures, he asked not to be buried in a prominent place within Winchester Cathedral, but outside in a simple tomb "where the sweet rain of heaven may fall upon my grave". The legend says after his remains were moved inside there was a great storm and it rained for many weeks after.
According to the old saying, if it rains on St Swithin's Day it will rain for the next 40 days. If St Swithin's Day is dry, the next 40 days will also be dry. No one takes the prediction literally - in fact, few take it seriously! - and there is definitely no statistical evidence to support the claim.
Weather experts say that since records began in 1861, there has never been a record of 40 dry or 40 wet days in a row following St Swithin's Day. The closest it might have got was in 1924 when (according to the Guinness Book of World Records) 30 of the 40 days after St Swithin's day were wet, but 13.5 hours of sunshine were recorded on July 15th.
There might, however, be a glimmer of truth in the legend. Summer weather here is shaped by the position of the jet stream. A northerly position in early July will make a drier, sunnier summer more likely, but a southerly position will often usher in a period of unsettled weather. St Swithin's day could well be a useful barometer.