Nature’s weather predictors

text and photo : Norma A. Hubbard  (December 2016)

A beautiful red sky always makes me think of the saying: “Red sky at night, sailors’ delight. Red sky in morning, sailors take warning”. Not sure when I first learned this rhyme, but as a sailor, I often wondered if this expression was a true predictor of the weather. Scientific studies seem to believe there is indeed truth to it, or at least more so than our groundhogs! We are surrounded by weather folklore or nature weather predictors. Many of us know some predictors and even trust them, such as, when animals produce thicker fall fur coats, it means a colder winter is coming, or an early spring can be predicted by the early arrival of geese. Who hasn’t heard of ‘the calm before the storm’, or ‘the smell of rain’? So let me add another nature predictor, one most of us have seen, but few of us may know, the woolly bear caterpillar.

According to The Old Farmer’s Almanac, weather folklore has it that these cute caterpillars can predict winter weather. Each caterpillar body has 13 segments. Legend has it that the wider the middle orange-brown section is, the milder our winter will be; conversely, with a narrow middle orange-brown section, we can expect a harsher winter. However, is this true or a myth?

Woolly bear caterpillars can be found in many cold regions, including the Arctic. As with other caterpillars, woolly bears hatch from eggs laid by a female moth, the Isabella tiger moth (Pyrrharctia isabella). Tiger moths are rather plain and most of us don’t pay much attention to them. This species will overwinter in its caterpillar form, the woolly bear, which can freeze solid and still survive.

Come spring, the caterpillars will spin a cocoon and emerge as a moth. In our area in late summer or early fall, woolly bears are everywhere, as the eggs hatch and the caterpillars go in search of a place to spend the winter. During the cold winter months, I have found them frozen in our firewood and on more than one occasion, one has crawled out of the logs as it warmed-up inside the house (not in the fire!)

One of the first studies on woolly bears was done by Dr. C. H. Curran in 1948. He had heard of the folklore and decided to test it. He collected samples of the caterpillars from Mountain State Park in New York State, counted the segments, then based on the segments, he predicted the weather. His prediction was correct. He continued his experiment for at least 8 years, trying to prove the woolly bears were reliable weather predictors. In the end it would seem, while fun to imagine, they may not be all that accurate. While there was not enough scientific evidence to support this legend, Dr. Curran did make the woolly bear famous as the most recognized caterpillar in North America; he even started a group called The Original Society of the Friends of the Woolly Bear.

If you want to decide for yourself if the woolly bear can predict the weather then take note, all the woolly bears I saw while taking pictures had wider brown sections. It is a small sampling, but it will be fun to check on this in the spring. Happy winter to everyone, regardless of the weather!

Source: Predicting Winter Weather : Woolly Bear Caterpillars, The Old Farmer’s Almanac (1999).