Ice saints and global warming

Spread the knowledge

Ice saints, when is it?

On May 11th, 12th and 13th each year we celebrate the Ice Saints – and not as the facetious picture of this article suggests, the ice breasts , or the holy ice , as we often hear! From one year to the next, the ice saints are therefore fixed.

Traditionally, Saint Mamert , Saint Pancrace and Saint Servais were asked by farmers to avoid the effect on the plantations of a drop in temperature that occurs at this time and can lead to a freeze period.

Once these dates are over, it is considered that gardeners no longer have to fear frosts and can replant all seedlings, tomatoes , eggplants and other frosty plants outdoors!

Why do not I see these names in my calendar?

The Church replaced the saints associated with gardening worries by others in 1960 – do not be surprised not to find Mamert, Pancrace and Servais in your calendars !

Where does this belief come from?

Is it true ? is it wrong? Should we trust this belief? There are in fact two ” scientific  ” explanations  for this phenomenon: 
– At this time, the orbit of the Earth crosses each year a disk of diffuse dust in the solar system formed by residues resulting from the formation of the planets. For a few hours, the dust would slightly obstruct solar radiation. Decreasing light intensity would be sufficient to influence ground temperatures . 
– In addition, the month of May is the end of the rapid circulation of winter weather systems. The sky is released more and more in the presence of anticyclones, the heat loss at the end of the nightis still important because the cloud cover no longer fulfills its role of conserving the heat accumulated during the day. The morning frosts could then still occur in this period.

But … With global warming?

In recent years, there has been a n and retreat of the last frost date – almost 3 weeks in 30 years! For example, in Strasbourg, the average last date was changed from April 22nd between 1951 and 1980, to April 3rd between 2000 and 2009! Still in Strasbourg, there has been a total of 16 days freezing since 1946 during the month of May in Strasbourg, but the last year that a freeze occurred in May, it was in 1985 !

One can therefore wonder if the rule of ice saints is still relevant – but caution always advises to keep your seedlings safe, and not to rush !

Dr. Kimberly Seltzer

Postdoctoral Scholar, UC Berkeley Research Assistant, MIT

Leave a Reply

Your email address will not be published. Required fields are marked *