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Extra - August 23, 2012
St Bartholomew's Day
A change in the weather?

By Philip Eden

Students of European history will know that St Bartholomew's Day falls on Friday, for the infamous massacre of Huguenots began on August 24, 1571. Students of meteorological history know it too, because there are almost as many old country sayings relating to this date as there are to any other. Most of them promise a change to drier weather following the frequent downpours which are so characteristic of July and August, along the lines of this one:

St Bartlemy's mantle wipes dry / All the tears Swithin can cry.

It reminds us that August 24 is exactly forty days after July 15 - St Swithin's Day - when any rain falling during the day (a 50-60% probability in mid-July) promises forty more rainy days. Although in practice rain has never fallen on all forty days, the weather pattern established around the middle of July will, more often than not, continue until late-August. The St Bartholomew's Day rhyme reassured our rural forebears that a change in the weather is bound to happen sooner or later.

An examination of readings made at Kew Observatory over the last 140 years shows a progressive drop in the average daily rainfall amounts during the last week of August and the first week of September, accompanied by a sharp rise in the frequency of completely dry days. An inspection of weather charts during the 20th century also shows an increase in the frequency of high pressure systems at about the same time.

There is nothing special, meteorologically speaking, about either St Swithin's on St Bartholomew's Day. Much of the country weather lore which has been handed down to us originated in the early Middle Ages when the church was intimately involved in people's everyday lives, so well-known saints' days were the obvious pegs on which to hang these snippets of seasonal information. Moreover, one should always remember the eleven "lost" days when we transferred from the Julian to the Gregorian calendar in 1752.

A rhyme relating to St Bartholomew's Day should therefore be regarded as appropriate to late-August and early-September in general rather than to August 24 in particular. It doesn't seem to be working this year, and the upcoming bank holiday weekend looks like being particularly unsettled. But as we head into September things should start to improve.

By Philip Eden

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