In primary school days, the approach of Saint Swithun’s Day would create a sense of trepidation. What would happen if rain fell on 15th July? Would a single shower on a single day mean that our six weeks of summer holiday were wet? Would our hopes of playing outside for day after day be washed away? Would our few chances of being on a beach be overshadowed by dark clouds and rainfall?

It is odd that a rhyme we learned should have had such power to affect our thinking. Every year, the lines would be recalled:

Saint Swithun’s day, if it does rain
For forty days it will remain
Saint Swithun’s day, if it is fair
For forty days it will rain no more

The medieval church capitalised on traditions that came to be associated with Swithun posthumously. Claims of him having miraculous powers to answer the petitions of those who sought his help led to various of his bones being incorporated in shrines in churches around the country.

Even in the 1960s, no-one at our school thought to ask the teacher why an Anglo-Saxon bishop of Winchester should be associated with the weather. No-one asked how could someone who was dead more than a thousand years affect what our summer holidays were going to be like? We never challenged the story, it was one of those traditions that people accepted. Just as we accepted many other things we were told.

Of course, Saint Swithun’s Day became significant because it was a day in mid-July, not because it had any link with a dead bishop. it is a time of year when weather can be settled and be warm and dry, or be unsettled and be cool and damp. What determines the likely pattern of weather for the days ahead is not the alleged powers of a saint, but the North Atlantic Oscillation (NAO).

The Met Office describe the NAO as “a giant see-saw across the Atlantic.” The two ends of the sees saw are described thus:

The common pressure features seen in the North Atlantic Ocean are for large regions of relatively high pressure centred over the Azores islands (west of Portugal, known as the sub-tropical or Azores high) and low pressure centred over Iceland (the sub-polar or Icelandic low). The NAO describes the relative changes in pressure between these two regions

Mid-July is a time when high pressure over the Azores has become established, pushing the jetstream northward, bringing warm dry weather to the British Isles, or it has not become established, allowing cooler, damp air to predominate.

The NAO was discovered by Sir Gilbert Walker in the 1920s, yet a century after the weather patterns were scientifically explained people are still talking about Swithun. Perhaps stories are more attractive than science.