If you are anything like me you will be thinking that after what felt like a prolonged grey, cold winter it feels like we should’ve turned a corner into summer. I suppose it’s mild at least and that’s almost enough to break out into a rendition of Reading Abbey’s own thirteenth-century composition ‘Sumer is icumen in’ … almost (you’d have to be a better singer than me for that though!).
Of course, as is always the case with the British weather, there’s no guarantee that it will stay warm, and it’s looking like this summer might be a bit of a washout, if this rain continues! But, what does any of this have to do with St Swithun, Winchester’s saintly ninth-century bishop?
Swithun (d. 863) was a Winchester churchman through and through, rising to the position of bishop of Winchester in c. 852-4. However, it is his posthumous work, as a saint and miracle worker, that Swithun is best known for. Among various miracles of aiding and healing those who petitioned him for his aid, a curious reputation has become attached to Swithun and his feast day, 15 July – oh, wait, that’s today!
This superstition is perhaps best summed up in the words of the following Elizabethan poem:
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 will rain na mair.
Where does this folkloric tradition come from? Well, the earliest-known textual reference of weather prophecy in relation to Swithun comes from a manuscript now held by Emmanuel College, Cambridge, that dates from the late thirteenth to early fourteenth century. However, the claim is backdated to the translation of Swithun’s tomb in the tenth century. This translation (the moving of a saint’s tomb or reliquary, or the moving of a saint into a new tomb or reliquary) occurred on the anniversary of Swithun’s death, his feast day, 15 July 971.
According to the later texts, the moving of his body from its initial burial place outside the church into Winchester Old Minster was proceeded by a storm that lasted (as the above poem states) for forty days. From this grew a tradition that if it rained on 15 July it would rain for the next six weeks.
Now, while Swithun is pretty amazing (I’ve always had a soft spot for him), it would be fair to say that this belief sounds like superstition. But, that doesn’t mean that there’s not some truth about the weather patterns between mid-July and the end of August. While I am all for encouraging my students (as well they know!) to understand sources and beliefs within their own time, this is one occasion where a little modern meteorological know-how actually adds to our understanding of this idea…
Why? Well, it has to do with the jet stream and its positioning. As meteorologist Derek Brockway (among others) has highlighted, the jet stream’s position in the middle of July can impact on the weather for the remainder of the summer. If it’s north of the UK, then we can expect warmer, drier weather. However, if it’s over the UK this causes low pressure and wetter weather.
Although it is unlikely to rain continually for forty days, prolonged wet weather during the summer can feel like it drags on. So, if it rains on St Swithun’s day will it rain until late August? Probably not. But, does this old association with the saint’s feast day and the weather have some grounding in meteorology? Yes.
So, let’s hope that this year we get good weather on 15 July and that both Swithun and the jet stream permit us a warm, dry summer!
Dr Ruth J. Salter is a lecturer in Medieval History at the University of Reading. Keep up with her blog ‘Medieval Miracles, Medicine and Miscellany’ here.
 This blog post can also be found on Ruth’s own blog.
 B. Yorke, ‘Swithun [St Swithun] (d. 863), bishop of Winchester’, Oxford Dictionary of National Biography, 23 Sept. 2004, (accessed 16 June 2021).
 J. Somerladd, ‘St Swithin’s Day 2018: Who was the British saint and why is he associated with the weather?’, Independent, 12 July 2018 (accessed 12 July 2021). NOTE: this article states the poem is twelfth century in origin but I am not aware of this being the case and the use of Middle English would suggest later.
 ‘St. Swithin’s Day’, Encyclopedia Britannica, rev. E. Rodriguz 30 April 2020 (accessed 12 July 2021).
 G. Cruikshank, ‘St. Swithin, Patron Saint of Umbrella Makers, vignette fragment from Plate 6 of Scraps and Sketches, Part II’, Ackland Art Museum (accessed 17 June 2021).
 D. Brockway, ‘St Swithin’s Day’, BBC Wales, 15 July 2009 (accessed 16 June 2021)
 Met Office, ‘What is the jet stream and how does it affect the weather?’, YouTube, 29 May 2018 (accessed 17 June 2021).
 ‘Hourly Forecast for Thursday 07/15’, Weather Underground, as of 11:00 12 July 2021 (accessed 12 July 2021).