ST SWITHIN'S Day is here again, and – joy of joys – it is still raining.

Legend has it that if it rains today, July 15, it will continue to rain for 40 days.

This is all to do with St Swithin, who, after his death in 863 AD, asked to be buried in the churchyard at Winchester Cathedral (then "Old Minster") so “the sweet rain from heaven might wet his grave". 

Unfortunately, this meant that, after a century or so, his resting place had become a "vile and unworthy grave" according to a group of devoted monks, who decided to move the body into the cathedral.

READ MORE: Yellow weather warning amid St Swithin’s Day rain

St Swithin asked to be buried in the churchyard at Winchester Cathedral (Image: Sophie Parr)

As soon as they tried to do so, however, a sudden deluge (allegedly caused by St Swithin's outrage) drenched the funeral party and it rained non-stop for nearly seven weeks, forcing the exhumation to be abandoned.

This is why if it rains on the day the monks tried to dig him up, July 15, it will rain for forty days. Alternatively, if it is sunny, the good weather will continue for the same period.

That is how the story goes, anyway. But after the MET Office issued a yellow weather warning today, do we really need to worry about a miserable end to the summer?

Fact or fiction?

St Swithin performed his fair share of miracles, including magicking a basketful of broken eggs back to their original condition.

While not everyone might believe that, it does seem that the St Swithin's Day phenomenon is not entirely a myth, with some scientific evidence backing the idea that the rest of the summer will be wet if it rains in mid-July.

SEE MORE: Heavy rain and thunder to hit parts of UK in ominous St Swithin’s Day forecast

This has to do with the Gulf Stream, which usually brings consistently fine summer weather until September.

However, if it drifts too far south, Arctic and Atlantic weather patterns can prevail, bringing a colder and wetter climate to the British Isles.

That said, 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.

From John Gay to One Day 

This belief (or superstition, depending on how you look at it) has persisted until the present day, with frequent references to the tradition in popular culture.

In 1716, John Gay, the author of The Beggar's Opera, published a poem entitled Trivia: Or, the Art of Walking the Streets of London, with the following lines:

"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 ‘twill rain nae mare"

More recently, St Swithin's Day played an important part in the plot of Netflix's hit TV romance One Day, based on the novel by David Nicholls.

Let's just hope that this year the legend remains firmly in the realm of fiction.