Banded Woolly Bear Predicts Mild Winter

Banded Woolly Bear | Pyrrharctia isabella
Banded Woolly Bear | Pyrrharctia isabella

Is it going to be a mild winter this year in British Columbia? You be the judge. According to some, if the orange band in the middle of a banded woolly bear (Pyrrharctia isabella) is wider than the black bands on the ends of the caterpillar it will be a mild winter. The opposite is the case if the orange band is narrower.

Apparently, winter severity prediction using banded woolly bears is about 80% accurate. Personally, I’m leaning toward a milder winter forecast which would also coincide with predictions of an El NiƱo winter. Scientists insist that the width of the bands has more to do with moisture conditions when the caterpillar is growing and the age of the caterpillar and is not related to weather prediction.

Banded Woolly Bear - A Sign of a Mild Winter?
Banded Woolly Bear - A Sign of a Mild Winter?

The banded woolly bear is the caterpillar of the Isabella moth which a member of the tiger moth or Arctiidae family. In the fall, the caterpillar chooses an appropriate place to overwinter and emerges with warmer weather in the spring. Some may be active on warmer days in February and March here on the West Coast. After feeding for a time, they form a cocoon from which the adult moth emerges later in the spring.

Regardless of whether or not they are accurate indicators of winter weather woolly bears are definitely interesting to watch. Keep an eye out for them on your walks this fall!


  1. Hi Dave,

    What an interesting post. I sure hope you’re right about a mild winter as I found last winter a little cold on the coast. At any rate, I would put more trust in these caterpillars than the local weatherman.

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