Can we trust popular sayings related to meteorology? Not very often. Here is an example, demolished by meteorological science and, therefore, by statistics. The saying? Christmas on the balcony, Easter on the firebrands. That is, if at Christmas it is hot and Santa Claus sees his sleigh sliding on the grass and not on the snow, then at Easter it will be cold and you will have to take out the poker to activate the fireplace (which does not heat well, I prefer a stove ).
Is this true? A trio of meteorology specialists (1) decided to take the subject seriously and subject it to the test of truth, that is, statistics. And he published his results in the journal of the French Society of Meteorology and Climate (SMF). To do this, of course, it was necessary to quantify, in terms of deviation from the climatological average, what is a Christmas on the balcony and what is an Easter on the blight. Forecasters have chosen a threshold of 1.5°C warmer for Christmas and 1.5°C colder for Easter. Once this quantification is done, search the Météo France archives to find out whether or not it is cold at Easter when it was hot at Christmas.
The result is unequivocal: the saying does not work most of the time. On a French scale, between 1947 and 2021, the saying is only true 11 times in 75 years. That is, three times in 20 years. These years? 1952, 1959, 1974, 1977, 1985, 1989, 1997; 2000, 2012, 2013 and 2014. And not once between 2015 and 2021.
A saying that is usually more false than true is already hard on popular belief. But there are worse things. They are the years of the “anti-saying”, Christmas in the fire, Easter on the balcony, that is, those in which the opposite of what he claims happens: it was warmer at Easter while at Christmas it was cold. The anti-saying is true in 1948, 1961, 1975, 1986, 2005, 2010. So, small consolation, less often than the saying.
Curious to see if the saying still held true on a regional scale, the trio abandoned the hexagonal thermal indicator to search the archives on a regional scale. Here again there is no ambiguity: the saying is not valid for any region. However, they note that this is a little less false in the north of France than in the south.
Finally, the trio became interested in the succession of the years 2010, 2011 and 2012. It shows the extent to which the years follow one another and are not alike. In 2010, all regions obey the antidictum, in 2011 four regions follow the dictum but the majority do not follow it. In 2012, most regions except the southern fringe of the country followed the adage.
Conclusion ? “Popular knowledge” about weather and climate can sometimes be correct, but when it risks being verified through a scientific approach, it risks being unmasked as beliefs without real foundations.
Sylvestre Huet
(1) Florianne Jean, National School of Meteorology, Simon Mittelberger and Matthieu Sorel, Directorate of Climatology and Climate Services, Météo-France.
