Page last updated at 10:50 GMT, Wednesday, 15 July 2009 11:50 UK

Is there any truth in St Swithin's lore?

Seaside goers on a rainy summer's day

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It's St Swithin's Day and folklore dictates that rain today means rain for the next 40 days. But, asks weather forecaster Philip Eden, is there any truth in the tradition?

St Swithin's is the day, but St Swithun was the man - a prominent character in 9th Century Wessex, born in or around the year 800 in Winchester.

A cleric and adviser to King Aethelwulf by the time he was 40, and in his later years a mentor to the young Alfred, history does not record whether Swithun had much aptitude for weather forecasting.

But it's the weather with which he is chiefly associated these days.

THE ANSWER
There's a grain of truth in St Swithin's lore
Weather often locks into a pattern in high summer, only changing when autumnal influences begin to appear in late August

Swithun's feast day is 15 July and weather lore holds that should it rain on this day, it will carry on raining for 40 days - until 23 August to be precise.

The 18th Century writer, John Gay put it this way:

"Now if on Swithun's feast the welkin lours
And every penthouse streams with hasty showers,
Twice twenty days shall clouds their fleeces drain
And wash the pavement with incessant rain."

But why should the story of Swithun have become so entangled with the meteorological elements? The legend explains it thus.

Swithun had a death bed request - to be buried, not with his episcopal predecessors in a prominent place within Winchester cathedral, but outside in a simple tomb, "where the sweet rain of heaven may fall upon my grave".

It is said that his successor bishop, Aethelwold, and perhaps King Edgar too, considered it unworthy for such an important figure to be buried outside. Instead a great ceremony was arranged to translate Swithun's remains to a magnificent shrine in the church.

Winchester Cathedral
Winchester Cathedral - spiritual home to Swithun

This ceremony took place on 15 July in the year 971, but was ruined by a tremendous rainstorm, which broke a period of drought. The weather remained abnormally rainy for several weeks thereafter.

This disaster was viewed as an indication of divine displeasure, and Swithun's bones were left where they were.

That's the fable at least. Historical and archaeological evidence only partially support it. Swithun's original tomb has been excavated, but it seems his remains were moved to a new site in the old minster, and subsequently to the new cathedral which replaced it at the end of the 11th Century.

Whatever the old rhymes may say about rain, meteorologists regard the middle of July as marking the warmest segment of the summer, on average. Mean daily maximum temperature values for London (Kew Observatory) between 1871 and 1980 exceed 22°C every day from 11 to 22 July inclusive, and then on scattered days until 17 August.

But what about that rain?

According to the old saying, if it rains on St Swithin's Day it will rain for the next 40 days. Less often quoted though, but an essential part of the traditional lore, if St Swithin's Day is dry, the next 40 days will also be dry.

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The times that we all hoped would last...

No-one takes the prediction literally, few take it seriously, and any statistical analysis will certainly support such scepticism.

I suppose it is possible that the wettest parts of the Western Highlands of Scotland - above Loch Quoich in Lochaber, for instance - will have 30 to 35 rainy days between 15 July and 24 August in the most inclement summers.

But Swithun was a Wessex saint, not a Scottish one, and the old weather lore applied originally to southern England.

At my own weather-recording site in Bedfordshire, the closest our unsuspecting ancient forecaster got was in 1985. Then, 30 of the 40 days following St Swithin's Day brought some rain, little or much, although 15 July itself was miserly in its offering with just a few light evening showers.

The obverse was almost proved in 1995 when only two of the 40 days following a dry Swithin produced rain, and then only small quantities of it.

Nearly as successful were 1990 and 1983.

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But those old enough to remember the heatwave summer of 1976 need to tread carefully when applying Swithin's rule.

Of the 40 days following 15 July, small amounts of rain fell on only two. St Swithin's Day itself was fine and hot, but a violent thunderstorm broke at midnight British Summer Time - 2300 by nature's clock - and over an inch of rain fell in an hour.

This was the most rain attributed to 15 July in the past 50 years.

There is much to be learnt from old weather fables, as we do not take the old rhymes and sayings literally. Our ancestors used them to pass on knowledge down the generations in an easily memorable form, at a time when ordinary folk could neither read nor write.

What Swithin really tells us is that our weather often becomes locked into a particular pattern in high summer, only changing when autumnal influences begin to appear in late August. Modern climatologists would largely agree with that.


Below is a selection of your comments.

In Germany it's called edible dormouse day (Siebenschlaefer) and it's on 27 June. However the weather is that day, it's supposed to be like that for the next seven weeks. Where I come from in Germany it's actually true most of the time, my parents seem to always have great weather right into autumn.
Franziska, Sevenoaks, UK

Here we hear the word "forty" which pops up a lot in folklore and the traditional use can be easily traced back to the bible where forty is used in abandon. The word "forty" here is a mistranslation from the Ancient Greek which should have said "many". But the tradition stuck and so we have forty this and forty that, rather than many. Did Ali Babar encounter forty thieves, for example, or just many of them?
Malcolm Smith, Porthmadog

But hasn't the day of the year that corresponds to 15 July changed since the Ninth Century because of the Julian-Gregorian calendar changeover in October 1582?
Mark, London

Mark, the papal bull was issued in 1582, the UK (and the then colonies) didn't change over till 1752. The real day would therefore now be backwards by about half the 11 days that were taken out, ie 10 July.
John Airey, Peterborough, UK

Last year we had heavy rain nearly every day for over a month after St Swithin's day. Scientists at that time told us it was because of a current in the Atlantic which settles into a pattern around this time every year. If it settles one way, it sends bouts of high pressure, if it settles another, it sends fronts of rain.
Phil, Calne, Wiltshire

I was lead to believe from weather men on the Beeb last year, that there was a basic correlation linked to the movement of the jet stream - if it hasn't moved by today, then we're likely to be in for a summer of above average precipitation. The current forecast would seem to align with this and certainly the jet stream hasn't moved above the south coast, where it would typically be above Scotland. The jet stream plays a big role keeping it low pressure.
Justin, Bournemouth

My wife's birthday is St Swithin's day, which means that day and every other day is full of sunshine, no matter what is happening outside, attested to be 40 years of marriage.
Philip Thomas, Merseyside



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