Swithin keeps eye on weather

Considering the good weather, it may have escaped your notice that yesterday was St Swithin’s Day, a feast day usually associated with rain.

In fact, the weather pattern forecast by conditions on the day can also mean a long spell of sunshine and dry days.

According to the old rhyme, the weather on St Swithin’s Day indicates what it will be like for the next 40 days — fair or foul:

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 mair.

St Swithin was the prior of Winchester Cathedral in England and was buried, according to his wishes, outside its walls “where passers by might tread on his grave and where the rain from the eaves might fall on it”.

His reputation as a weather saint arose from the resiting of his body from this lowly grave to its shrine within the cathedral having been delayed by incessant rain.

According to the website Weather Online, there is a scientific basis to the legend of St Swithin’s day.

Around the middle of July, the jet stream — a band of air currents encircling the globe — settles into a pattern which holds steady until the end of August. When the jet stream lies north of the British Isles then continental high pressure is able to move in; when it lies across or south, Arctic air and Atlantic weather systems predominate.

“The meteorological interpretation is quite straightforward,” says Weather Online. “The position of the frontal zone around the end of June to early July, indicated by the position of the jet stream, determines the general weather patterns (hot, cold, dry, wet) for the rest of the summer. Like a little stream in its bed, the frontal zone tends to ‘dig in’ shortly after the summer solstice.”

As the path of our weather systems is controlled by the jet stream, a more southerly location of the frontal zone is likely to bring rather unsettled, wet and cool weather, which is what has predominated for the past six years or so. On the other hand, a frontal zone shifted further to the north will help the Azores high to build over western Europe, thus bringing dry and pleasant weather to the UK and Ireland.

The St Swithin’s Day rule is also known in other western European countries. In France they say: “Quand il pleut a la Saint Gervais il pleut quarante jours apres” — “If it rains on St Gervais’ day {Jul 19], it will rain for 40 days thereafter”.

In Germany the Siebenschlaefer, or seven sleepers day (Jul 7), refers to the weather patterns of the following seven weeks.

Meanwhile, no amount of praying to St Swithin will help against a sting from the dreaded weever fish. Swimmers and surfers should be wary of the venomous fish, which they may encounter due to the new moon and spring tides this month.

A new moon will lead to spring tides, which means that swimmers and surfers will have to venture further out from the beach into the area where the weever lives.