Today is St Swithun’s day. If it rains, folklore dictates that we’ll have 40 days of rain. If it’s dry and sunny it will be 40 days of fair weather. It’s complete nonsense, but we like to acknowledge these myths and legends all the same. But who was St Swithun and how did the weather myth come about?

Swithun (sometimes spelled Swithin) was an Anglo-Saxon priest who became bishop of Winchester in 852 CE.

Not much is known about his early life and he is barely mentioned in any manuscripts written during his lifetime.

When he died in 862 (some say it was 861), he was apparently buried just outside the churchyard of the cathedral at his own request, so that passersby could walk over his resting place and the rain could soak into the soil around him.

In 971 his remains were exhumed, and he was moved indoors into a newly created shrine.

Legend has it that on the day of the move there was a great storm and subsequently, there were then 40 more days of rain.

The curse is summed up by an old poem, “St Swithun’s day if thou dost rain, for 40 days it will remain, St Swithun’s day if thou be fair, for 40 days twill rain nae mare”.

There is a connection between changing weather patterns and mid-July, but this is in no way linked to the myth of St Swithun.

During the summer, the jet stream – winds that travel from west to east five to seven miles above the earth’s surface – usually flows just north of Britain and during summer can lead to drier, hotter weather.

The interesting thing is that links between saints and weather lore are not restricted to the UK and St Swithun.

In Flanders, the Flemish region of Belgium, July 6 is St Godelieve’s day and that has a similar weather myth. In France, St Medard (June 8), Urban of Langres, and St Gervase and St Protais (June 19) are all said to influence the weather in a way that is almost identical to that of St Swithun.

The likelihood is that the change in weather conditions brought about by the jet stream may have been artificially attached at some point to the saints’ days rather than the other way around.

All it takes of course to spoil a beautiful idea is for the predictions to be shown to be false. They have been, many times.

Twice, in the 20th century the legend was completely turned on its head. In 1913 a 15-hour rainstorm in London was followed by 30 days without rain.

Then, in 1924 on St Swithun’s day there were over 13 hours of sunlight with no rain in London.

This was followed by 30 days of rain.

There is another issue with the story of St Swithun. None of the legends can be traced back directly to the period when it was supposed to have originated.

There’s a mention of the tale in a 14th century manuscript that remarks on a major storm that happened on St Swithun’s day in 1315, but that’s it.

Norway also celebrates St Swithun’s day, but on July 2 as did the Welsh in medieval times.

His name is dedicated on 40 or so Churches, mainly in the South East. A few schools, such as St Swithun’s in Winchester, are named after him.

To become a saint, you need to have performed miracles. One of Swithun’s miracles was to restore a basket of eggs that had been broken.

The story is that one day as Swithun was walking over a bridge that led to the market, he came across a woman crying. Asking her what was wrong she told him that she had been carrying a basket of eggs across the busy bridge and they were knocked out of her hands by someone and broken.

Taking her by the hand he told the woman not to worry. When she picked up the basket, the broken eggs were all whole again.

Probably the most famous folklore associated with the weather is Groundhog Day on February 2, made famous by the film of the same name.

Legend has it that if an emerging groundhog sees its shadow on a clear sunny day it will retreat into its burrow and spring will be delayed for six weeks.

However, if it’s cloudy and there is no shadow, spring will come early. The origin for this folklore seems to come from Germany where badger day has the same story on February 2. It came to the US via the Dutch settlers in Pennsylvania.

However, as with St Swithun, there is no evidence that a groundhog can predict the change of seasons or the weather.