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June 15th has special place in weather folklore

By Skip Rigney

Did you know that for our weather forecasting ancestors the weather today, June 15, was a critical predictor of the upcoming month?

These days, people who want to become weather forecasters go to college and take courses in physics and mathematics, learn to analyze measurements from satellites and radars, and practice deciphering daily output from some of the largest computers in the world used to solve the complex equations that describe the processes going on in the atmosphere.

Back in the day, before anyone had dreamt of calling himself a meteorologist, the path to becoming a weather forecaster was a little less arduous. But, it certainly wasn’t less important.

In 1800 over 90 percent of the world’s people lived in rural areas. That was true in every country on earth according to Hannah Ritchie and Max Roser who published their research on urbanization this year at OurWorldInData.org.

It’s a safe bet that most of those rural folks were involved in farming, and farmers have always taken a keen interest in the weather. Year after year, generation after generation, they observed the weather for hints about what the future might bring.

Even without equations and satellites, our ancestors were able to discover some correlations that turn out to actually have some predictive skill when it comes to the near-term weather.

One of these correlations is summarized in the famous rhyme, “Red sky at night, shepherds’ delight; red sky in morning, shepherds’ warning.” Sailors have an almost identical version of the adage, an indicator of another profession with an intense, vested interest in weather forecasting. This insight is at least 2000 years old. Jesus’ use of a variant of this proverb to chide his opponents for their ineptitude in reading the signs of the times is recorded in Matthew 16:2-3.

The physics of why this particular saying is often accurate involves the movement of high and low pressure weather systems, and the scattering of sunlight through dusty and moist air. Scientists at NOAA’s Earth Systems Research Laboratory explain the details in a short and easy-to-understand article at https://www.esrl.noaa.gov/gmd/grad/about/redsky/

Farmers aren’t just interested in the weather for the next day or two. They also want to know the weather for the upcoming month and season. Over time in Europe, it came to be believed that weather on certain days foreshadowed what lay ahead in the coming weeks.

These special days became known as the ten Days of Prediction. All of them were eventually known by their place on the church calendar. Of June 15, it is said, “If St. Vitus’ Day be rainy weather, it shall rain for thirty days together.”

I confess, until researching this article, I didn’t know who St. Vitus was, or that today is his feast day, or that Europeans of old from England to Estonia thought June 15th’s weather was a prequel to the coming month. While some of the shorter-range forecasting proverbs such as “Red sky at night,” have proven to have some validity, I’m not aware of any evidence for the accuracy of folklore forecasting for months or seasons.

So, with all due respect to St. Vitus, even if you experience a widely scattered shower today, I wouldn’t jump to any conclusions about the next month.