The ice saints, what?

Published on May 12, 2006 at the base. Updated in 2007, then in 2014, then in 2016. because the Saints of ice, it's cyclical. So this post also.

I was always taught, instilling me the joys of gardening, that should never be able to plant his tomatoes until mid-May: because of the ice Saints^[1]. I, at first, smiled inwardly: if it's tradition, respect the, and don't antagonize the elders.

As for the days where, based on the Moon, there is no especially not sow vegetables "to map", otherwise they will not grow. It is written in the Messenger lame, it's so not anything.

And, over time, I still realized that, the week before mid-May, there was indeed regularly a few days back from the cold and rotten time^[2]. So, I does not crash my tomatoes before mid-May. The ancients were right.

But what are these Saints of ice? The three best-known are Mamertus, Pancras, Servais and 11, 12 and 13 May. There are also urba^[3]n. But it isn't necessarily what interests us most: why is it so cold during the ice Saints? My Cartesian mind forces me to think that there is a rational explanation for Cel… I found it in several places. But the original source must be here. I quote from:

(…) The inclination of the orbit of the earth around the Sun is very slightly different from the average orbital plane of all the planets. However, a drive extremely diffuse dust accompanies the latter in their multi-seculaire course, formed by particles trapped by debris from the formation of the planets at the dawn of their existence as well. Nearby the 12 or may 13 of each year, the Earth is brought through this disc which, for a few hours, very slightly impeded solar radiation. The decrease of their intensity is unobservable without measuring instruments are extremely sensitive, but sufficient to influence the delicate mechanisms of meteorology of our globe. (…)

So it was that! Apart from that, on Wikipedia, we can see that this kind of explanation is debate: for example, Keres says:

I doubt the physical explanation that I found… I don't find it very clear in regard to the fact that the Earth passes this dust may 12 and therefore which coincides well with our ice saints, but as explained does not coincide with what was said before the new calendar. If I understand the reasoning, before the date of the saints was not in line with the cycle of the Earth. That means the saints of ice could be found are in the winter, are in summer, spring or fall. So either the ice saints have a true meaning today and absurd in the past, either the phenomenon does not exist.

or even Pierre cb:

The explanation is that pure ignorance of meteorology. Dust can affect the energy balance and help to cool slightly, but it is a global phenomenon. But these sayings are very local and inapplicable in Quebec or in Florida for example. The mid-latitude atmospheric circulation explains that these dates be separates the time of the last frost around the France.

Therefore, we may never know the reality…