Woolly Bear Caterpillar and 10 Signs of a Rough Winter
Quick Reference: Reading a Woolly Bear Caterpillar
- The folk rule: the wider the black bands on each end, the harder the winter ahead. A wide rusty brown band in the middle is said to mean a milder one.
- More black than brown: folklore calls for a colder, snowier season.
- A narrow orange band: a warning of heavy snow.
- Fat, fuzzy, and everywhere: lots of caterpillars with heavy coats point to a bitter, cold winter.
- The honest caveat: scientists say the bands track the caterpillar’s age and last season’s weather, not the winter to come. Enjoy it as folklore, then check the forecast.
Every fall the same question lands in our mailbox. There is an old folklore about caterpillars, a reader writes, so what does the coloring of a woolly bear mean? I have seen some that are mostly brown. Does that mean a hard and snowy winter in the East? It is a fair question, and it has a long, colorful answer. Next to Punxsutawney Phil, the lowly woolly bear caterpillar is the most famous weather prognosticator in the animal kingdom, and folks have read its stripes for generations.
What Is a Woolly Bear Caterpillar?
The woolly bear, also called the woolly worm in the South, is the fuzzy fall caterpillar you see hurrying across country roads and driveways in September and October. It wears a coat of stiff bristles, black on both ends and rusty brown in the middle. Come spring it spins a cocoon and emerges as the Isabella tiger moth, a small yellow-orange moth you have likely seen circling a porch light. It is a favorite of anyone who likes to read the season in the animals before checking the long-range forecast.
How to Read a Woolly Bear Caterpillar
Legend has it that the color and thickness of a caterpillar tells you what kind of winter is coming. Here is how the old rule goes. The woolly bear signals a bad winter if there are a lot of them crawling around, if it has a heavy coat, and if the black band on its back is wide. The more black than brown it shows, or the wider the black stripe, the worse the winter. A narrow orange band in the middle warns of heavy snow. And if this fellow is fat and fuzzy, folklore says to expect bitter cold.
So what about our reader’s mostly brown caterpillar? By the traditional reading, a broad brown middle band points the other way, toward a milder, gentler winter rather than a hard and snowy one. Two woolly bears found in the same yard on the same afternoon can carry very different bands, which is part of the fun, and part of the reason to take any single caterpillar with a grain of salt.
Where the Woolly Bear Legend Comes From
The modern woolly bear legend traces back to one curious scientist. In the fall of 1948, Dr. C. H. Curran, a curator of insects at the American Museum of Natural History, drove up to Bear Mountain State Park in New York to collect caterpillars and measure their brown bands. He wanted to see whether the folk rule held up. His small counts hinted that wider brown bands went with milder winters, and a newspaper reporter along for the trip helped turn the study into a national story. Curran repeated the outings for several years, more for the autumn fun than for hard science, and the woolly bear has been a fall celebrity ever since.
The tradition is celebrated to this day. Banner Elk, North Carolina, and Vermilion, Ohio, both throw yearly Woolly Worm festivals every October, complete with caterpillar races and an official reading of the winner’s bands. It is folklore worn with a wink, and it keeps a piece of country weather wisdom alive for the next generation.
What Science Says About the Bands
Here is the measured caveat. Entomologists say a woolly bear’s bands reveal its age and the weather it has already lived through, not the winter still to come. The brown band widens each time the caterpillar molts, so an older, well-fed caterpillar simply shows more brown. A wet, mild growing season can also shift the coloring. The National Weather Service notes that the bands are a good story but a poor forecast, and it lays out the science in its own woolly bear caterpillar writeup. We build the Almanac’s long-range outlook on a math-based formula of sunspots, moon phases, and planetary positions, not on caterpillar coats, and we still love the folklore for what it is.
10 Signs of a Rough Winter From Nature
The woolly bear is not the only critter said to read the season. If you want to be your own weather forecaster, here are 10 classic signs of a rough winter that country folks have watched for over the years.
- Very thick onion skins or corn husks.
- Woodpeckers sharing a tree.
- Early arrival of crickets on the hearth.
- Spiders spinning larger webs.
- Lots and lots of acorns.
- Raccoons have thick tails.
- Squirrels gather nuts early in the year.
- Pigs gather sticks.
- Frequent halos around the sun or moon.
- Heavy and numerous fogs in August.
Some of these carry a kernel of truth. A halo around the sun or moon comes from high, icy clouds that often ride ahead of a storm, so that one has real weather behind it. Others, like pigs gathering sticks, are pure country charm. Either way, they are worth watching, and half the pleasure is keeping an eye out. Track the halos against the full moon dates, and use the Gardening by the Moon Calendar to time the chores each sign hints at.
Reading the Signs Across the US and Canada
The same sign can mean different things depending on where you stand. A heavy acorn year in New England is read as a warning long before the first hard freeze, while a Gulf Coast gardener may watch the fog and the onion skins instead. Here is how the folklore tends to travel by region.
None of these are guarantees, and a mild winter can follow a bumper acorn year just as easily as a harsh one. Read them the way our grandparents did, as friendly hints from the yard, then plan around the numbers.
Keep Your Own Weather Journal
The best way to test any of this is to write it down. Jot the date you spot your first woolly bear, sketch its bands, and tally the acorns underfoot. Note the fogs in August and the first crickets by the hearth. Come March, compare your notes to the winter you actually got. There are many other things to observe out there, so if you see any, pass them along. Over a few seasons you will build your own almanac of the land around you, and you may be surprised how often the old signs earn a nod. For a peek at where the Almanac lands, browse our extended forecast and pick the Best Days for the chores the season brings.
Woolly Bear Caterpillar and Winter Signs: Frequently Asked Questions
Can a woolly bear caterpillar really predict winter?
Not reliably. The folklore says wider black bands mean a harder winter and a wide brown band means a milder one, but entomologists have found the bands reflect the caterpillar’s age and the weather it has already lived through, not the season ahead. Enjoy the woolly bear as a bit of fall fun, then check a real long-range forecast for planning.
What does a mostly brown woolly bear caterpillar mean?
By the traditional rule, a broad rusty brown middle band points to a milder, gentler winter rather than a hard and snowy one. Keep in mind that the brown band naturally widens as the caterpillar ages and molts, so a mostly brown woolly bear is often just an older one.
What do the black bands on a woolly bear mean?
Folklore holds that the wider the black bands on each end, the harsher the winter, and the more black than brown a caterpillar shows, the worse the cold. A narrow orange band in the middle is said to warn of heavy snow. It is a charming rule, but two caterpillars in the same yard can show very different bands.
What are the classic signs of a rough winter from nature?
Country lore watches for thick onion skins and corn husks, lots of acorns, squirrels gathering nuts early, thick-tailed raccoons, spiders spinning larger webs, woodpeckers sharing a tree, crickets on the hearth, pigs gathering sticks, halos around the sun or moon, and heavy fogs in August. A few, like the halos, have real weather behind them, while others are pure country charm.
Where did the woolly bear winter legend start?
The modern legend grew from Dr. C. H. Curran, an insect curator at the American Museum of Natural History, who measured woolly bear bands at Bear Mountain, New York, starting in 1948. His small counts and the newspaper coverage that followed made the caterpillar a national weather celebrity, and towns like Banner Elk, North Carolina, still hold Woolly Worm festivals each October.
How does the Farmers’ Almanac actually predict the weather?
We use a math-based formula that weighs sunspot activity, the position of the planets, and the phases of the Moon, a method the Almanac has followed for more than 200 years. It is not built on caterpillar coats or acorn counts, though we enjoy the folklore alongside it. See our long-range forecast to compare the outlook for your own town.
Peter Geiger
Peter Geiger is the Editor Emeritus of the Farmers' Almanac. Read his full biography.
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tons of crickets in the house ,saw a two woodpeckers on the same tree man i would like to see a good snow in va this year looks like it to me not to mention all them huge caterpillers
I live in central Ohio and have seen a few woolly bears around my porch. They seem to be heading north and have a large orange stripe not too much black. I hope it is a mild winter ,we had a mild summer. Thanks!
Upstate NY we are having very furry caterpillars with a really wide rust strip and short black ones this year. Usually we get tons and tons of snow so maybe this year we will have a repreave hopefully lol.
In southern Ontario I have seen furry brown caterpillars with one wide black stripe on each end of their body. What does this mean. From the information, I would say a cool winter with snow, is this correct?
Yesterday we had 10 very furry caterpillars with wide black strips on the backs. 9/4/09. Great, it doesn’t usually get too bad here in southern Virginia, looks like it will be different this year!
We just found a caterpillar walking on the kicthen floor.1/1/2009