Rutronik News

If it rains on the feast day of St. Denis, it will certainly be a wet winter

  Newsletter Article

“Crap weather!” How often have you had that thought in the last days and weeks? This past summer was rather subdued and September tortured us with mostly gray, rainy days and even a few severe storms. Bad weather affects our mood and can sometimes make even a Friday feel like a Monday, especially when the weather forecast is wrong. Who hasn’t looked forward to a warm fall day and woken up to a downpour, you can just feel your mood take that same plunge that the temperatures did. And who's at fault? The meteorologists or, as the band B*Witched sang in the 90s, “Blame it on the weatherman.”

Since the beginning of time, humans have battled the weather. They fight against it, try to forecast it and control it – and all those efforts have thus far failed. In the Stone Age, weather influenced the success of the hunt. In the ancient world, humans prayed to their weather gods, like Thor or Taranis, to ensure favorable weather so that the crops would grow and enemies would fall quickly in battle. They consulted seers, augurs and oracles. They sacrificed a lot of time, nerves and even the odd virgin for a favorable forecast. Of course, all for naught. During the first Punic Wars, after the sea Battle of Cape Bon, 300 of 370 ships from the Roman fleet went down in a horrendous storm, with 100,000 soldiers lost at sea. And God was hardly more merciful in the Middle Ages. Due to the dreadful weather characterized by a series of long winters and rainy summers, famine prevailed in Europe from 1437 to 1440.

Not until the Renaissance did people finally begin to grasp that nature itself and not God influences the weather. In 1508, weather-related folk sayings – mostly in rhyme – were written down for the first time in the book “Bauernpraktik,” the German equivalent of the “Farmer's Almanac.” These folksy farmers' sayings were intended to help forecast the weather to some degree. The saying quoted in the title “If it rains on the feast day of St. Denis, it will certainly be a wet winter” refers to St. Denis of Paris and his feast day on October 9. It will be interesting to see if this farmers' saying comes true. However, the accuracy of such sayings suffered heavily when Europe switched over to the Gregorian calendar.

In 1592, Galileo Galilei developed the first thermometer and, in 1762, Benedictine monks founded the first weather station at a monastery in Austria. Nowadays, a CrayXC40 supercomputer in Offenbach am Main speculates over current weather forecasts for the German weather service. Yet despite a closely woven data network – there is a hub every 2.8 kilometers in Germany to help forecast the weather – it is still impossible to predict the weather with one hundred percent certainty.

We see examples of this on a regular basis: In September, the “Katwarn” app (a German information and warning system for catastrophes) for our headquarters in Ispringen issued a warning for major storm. So, we closed windows, turned on the heating and hoped that the storm would pass by evening. Then nothing happened. Except for a few tired raindrops and a light wind, there was no sign of any freak weather systems. Even the roofers up on the roof were able to continue working without a second thought. Luckily – and better this than the other way around.


There is no such thing as a highly accurate forecast and there will not be one in the future either. Regardless of how tightly researchers weave their network of acquired data – even the tiniest of changes can create chaos. This is what we call the butterfly effect that meteorologist Edward N. Lorenz described in 1972.

We cannot accurately predict the weather. And we cannot change it either, even if we wanted to, though not for lack of trying. The Chinese government used silver iodine to ensure that no raindrops fell on the Olympic Games in Beijing. However, the method is not fool-proof – as a countermeasure against a long drought, Beijing wanted to generate rain storms over a certain area. The result was a snowstorm in the capital city that created traffic chaos.

So humans can interfere to a certain degree. But can they influence the weather? Yes, unfortunately, they can – indirectly through climate change, but not at the press of a button. And that's a good thing. Those of us stuck in an office may already be wishing again for sunny 80°F weather and it's only September, but farmers have a totally different outlook.

And don’t forget that weather is always a harmless topic for small talk. What else is there to talk about? Politics? No, preferably not. Then perhaps a gray September after all!