Woolly Worms: The Original Winter Weather Outlooks

Woolly Bear Caterpillars Can Allegedly Predict Winter Weather

A banded woolly worm caterpillar. Flickr user welovethedark

Every October, NOAA's Climate Prediction Center releases a winter outlook to give the public the best possible scientific prediction of how the winter may shape up across the nation; but in the pre-NOAA days, folks got this same information from a more humble source--the Woolly Bear caterpillar.  

Called "woolly bears" in the Midwest and Northeast, and "woolly worms" in the Southern U.S., Woolly Bear caterpillars are the larvae of Isabella tiger moths. They're common to the United States, northern Mexico, and the southern third of Canada, and are easily recognized by their short, stiff bristles of reddish-brown and black fur.

How to "Read" a Woolly's Colors

According to folklore, the woolly worm's coloring is said to indicate how severe the coming winter will be in the local area where the caterpillar is found. The Woolly Bear caterpillar's body has 13 distinct segments. According to weather lore, each one corresponds to one of the 13 weeks of winter. Each black band represents one week of colder, snowier, and more severe winter conditions, whereas orange bands indicate that many weeks of milder temperatures. (Some even believe that the position of the bands which part of winter. For example, if the tail end of the caterpillar is black, it means that winter's end will be severe.)  

Two other versions of this folklore exist. The first relates the severity of winter to the thickness of the caterpillar's coat. (Thicker coats signal colder winters, and a sparse coat, milder winters.) The final variation deals with the direction in which the caterpillar crawls. (If a woolly crawls in a southerly direction it means he's trying to escape the cold winter conditions of the north. If he travels on a northward path, that indicates a mild winter.)  

Significance of Solid-Colored Woolly Worms

Not all woolly worms have alternating orange and black markings. Occasionally, you'll spot one that's all brown, all black, or solid white. Like their brown and black relatives, they too have :

  • Orange: Just as reddish-brown segments signal a week of mild temperatures, an all brown caterpillar suggests an overall mild winter with above-normal temperatures and insignificant snowfall.
  • Black: An all black caterpillar signals the onset of a very hard upcoming winter.
  • White (sand-colored): White woolly worms are said to predict winter snowfall. Spotting one is supposedly a strong indicator that heavier than average snows -- or even a blizzard -- can be expected in the region during the winter season. 

How Fame Found the Woolly Worm

The woolly worm's talent was first discovered in the late 1940s by Dr. Charles Curran, former curator of insects at New York City’s Museum of Natural History. As the story goes, Dr. Curran measured the coloration of woolly bear caterpillars between 1948 and 1956 at Bear Mountain State Park. During those years, he found that 5.3 to 5.6 of the observed caterpillars' 13 body segments were orange. As his counts suggested, the winters for each of those years turned out to indeed be mild. A reporter friend of Curran's "leaked" his forecasts to a NYC newspaper, and the publicity the story generated made woolly bear caterpillars a household name.

Is the Folklore True?

Dr. Curran found that the width of reddish-brown fur correctly matched the winter type with 80% accuracy. While his data samples were small, for some people this was enough to legitimize the folklore. However, for the majority of today's professionals, it isn't sufficient data. They argue that not only is a woolly bear's coloring based on its age and species, but also that it would take researching an awful lot of caterpillars in one place over a great many years in order to make any conclusions about woollys and winter weather.

One thing most can agree on is that regardless of whether or not the folklore is true, it's a harmless and fun autumn tradition to take part in.

When and Where to Spot Woolly Worms

Woolly worms are usually seen in autumn on sidewalks and roadways. If you do meet one, don't expect it to hang around for long. Woollys are busy creatures, always "on-the-go" searching for a cozy home underneath a rock or log to overwinter in. They move pretty fast too (as worms go)!  

One sure-fire way to meet a woolly is to attend a woolly worm festival.

2016 Woolly Worm Festivals

Like the groundhog, woolly worms have become so popular, several festivals have sprouted up across the United States to honor them. The longest-running festivals are celebrated in: 

  • Vermilion, Ohio. Ohio's annual Woollybear Festival is one of the longest-running in the US. The festival started more than four decades ago, when TV weatherman, Mr. Dick Goddard, proposed the idea of a celebration built around using the worm to forecast the upcoming winter. He still hosts the festival to this day. This year's festival is scheduled to be held October 2, 2016.
  • Banner Elk, North Carolina. Held every third weekend in October. This year's 39th Annual Woolly Worm festival dates are October 15-16, 2016. 
  • Beattyville, Kentucky. Beattyville's Woolly Worm Festival is always the last full weekend in October. This year's 29th annual festival will take place October 21-23, 2016. 
  • Lewisburg, Pennsylvania. Currently in its 19th year, this year's festival will take place on October 15, 2016.

If you're a fan of woolly worm festivals, let us also recommend these weather-focused festivals.

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Your Citation
Means, Tiffany. "Woolly Worms: The Original Winter Weather Outlooks." ThoughtCo, Jul. 31, 2021, thoughtco.com/woolly-bears-and-winter-outlook-3444522. Means, Tiffany. (2021, July 31). Woolly Worms: The Original Winter Weather Outlooks. Retrieved from https://www.thoughtco.com/woolly-bears-and-winter-outlook-3444522 Means, Tiffany. "Woolly Worms: The Original Winter Weather Outlooks." ThoughtCo. https://www.thoughtco.com/woolly-bears-and-winter-outlook-3444522 (accessed March 20, 2023).