top of page

Woolly Bear Caterpillars - Winter Forecasters?

For as long as I can remember, I can recall the old wives tale surrounding the pretty, rust colored belts of fuzz on these little worms and the severity of the winter ahead - my grandmother said it this way: "If the brown belt's wide, the winter's mild".

In fact, every variation of these little caterpillars (known as Wolly Bear Catterpillars) seems to have some sort of assigned meaning for the season ahead. But does this have any bearing on actual forecasts? This speculation began in the late 1940s, when an ambitious scientist went up to Bear Mountain, New York to study these critters, and seemed to, at first, notice this correlation that has become the folklore of today - due to this, he actually committed 8 years of study to figuring out if this correlation was true!

The results? No such luck. There appeared to be no evidence of this correlation. Unfortunately, the story had already been broken in the news, and we all know that once that floodgate is opened, it never shuts. Interestingly enough, however, these caterpillars can tell us about the PREVIOUS winter using their coats! Research indicates that, when born in the spring, while born black, the temperature and environment they are born into impacts the amount of rusty brown they develop on their coat. Keeping with the folklore, it appears that the rusty color indeed DOES grow during warmer seasons, but only after the fact, acting as something of a time capsule for seasons past.

One science-based seasonal forecasting tool, however... the Climate Prediction Centers seasonal outlook. The CPC outputs these 3 month spanning predictions in attempt to understand and predict the season ahead, using various forms of climatology and forecast models, and have a fairly decent track record - definitely more than the 50/50 that the woolly worms tend to bat! This winter? It's looking like, at least for us in the Valley, the odds are leaning towards a very slightly above average winter in terms of Temperature, as well as for precipitation chances. This is subject to change, but would make sense given the La Nina nearby.

But who knows? Maybe the rusty Caterpillars predicted it first!

634 views0 comments
bottom of page