Can the woolly bear caterpillar really predict winter weather?

PORTLAND, Ore. ( KOIN ) — If you’re out and about on the trails this fall, you might run into a fuzzy black and orange fellow inching across your path.

The woolly bear caterpillar, also known as the fuzzy bear caterpillar or the woolly worm, has fuzzy bristles that are black on both ends with a band of orange in the middle.

Meteorologist Kelley Bayern of Nexstar’s KOIN spotted one on a recent fishing trip on the Crooked River in central Oregon.

The caterpillar isn’t only cute, it comes with a great and powerful lore — but is it true?

The Weather Myths

One theory suggests that if the caterpillar’s coat is especially “woolly,” a cold winter is likely, the National Weather Service explains . Another theory relies on the direction the caterpillar is traveling when you see it. If it’s moving south, it’s trying to escape from colder winter conditions in the north. But if it’s heading north, we’re in for a milder winter.

According to other folktales, the amount of orange or rusty color on the woolly caterpillar could signal the severity of the upcoming winter where it was found. If the caterpillar is mostly black, with a more narrow orange band, the upcoming winter may be colder, snowier, and overall more harsh. And vice versa: a woolly bear caterpillar with a wider orange middle section will predict a calmer winter.

The woolly bear caterpillar Bayern found in central Oregon seems to be predicting a harsher winter since the orange bands were fairly narrow. Perhaps it has tapped into an upcoming La Niña pattern coming this winter, which is something that can correlate to a wetter and colder pattern in the Pacific Northwest across the colder months.

Woolly Bear Debunked

There are two generations of these caterpillars each year, one in spring and another in fall. The fall caterpillars are the “best forecasters,” or the most colorful. Woolly bears feed in the fall in preparation for winter hibernation, where they nearly freeze solid. When springtime arrives, they thaw and become active again.

As fun as this myth sounds, a caterpillar simply cannot predict the weather (or Bayern and meteorologists across the country would be out of a job). The caterpillar’s color is based more upon its recent diet and age. A better growing season may result in a larger caterpillar with more black coloring.

The caterpillar Bayern found, seen below, was massive, about three inches long, and likely an older gentleman due to its size and black coloring. She named him Greg.

After waking from its winter hibernation, the caterpillar will feed through spring, then cocoon and emerge as an Isabella tiger moth. Isabella tiger moths are found throughout the U.S., though not in Hawaii and Alaska.

Even though the woolly bear caterpillar may give Punxsutawney Phil a run for his money, the best winter forecast will come months from now when we reach the cold season.

The latest three-month outlook from NOAA shows most of the country is leaning toward a warm fall season – October through December – with chances generally growing stronger the further south you live.

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