Learn more and buy the 2015 Old Farmer's Almanac!

Predicting Winter Weather: Woolly Bear Caterpillars

Related Products

Your rating: None Average: 3.6 of 5 (200 votes)

The woolly bear caterpillar—with its 13 distinct segments of black and reddish-brown—has the reputation of being able to forecast the coming winter weather.

Here are the history, facts, and lore about this legendary caterpillar.

How the Woolly Bear Became "Famous"

  • In the fall of 1948, Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City, took his wife 40 miles north of the city to Bear Mountain State Park to look at woolly bear caterpillars.
  • Dr. Curran collected as many caterpillars as he could in a day, determined the average number of reddish-brown segments, and forecast the coming winter weather through a reporter friend at The New York Herald Tribune.
  • Dr. Curran's experiment, which he continued over the next eight years, attempted to prove scientifically a weather rule of thumb that was as old as the hills around Bear Mountain. The resulting publicity made the woolly bear the most recognizable caterpillar in North America.

What is the Woolly Bear?

The caterpillar Curran studied, the true woolly bear, is the larval form of Pyrrharctia isabella, the Isabella tiger moth. See and share this picture of a woolly bear!

Here is more background:

  • This medium-size moth, with yellowish-orange and cream-colored wings spotted with black, is common from northern Mexico throughout the United States and across the southern third of Canada.
  • As moths go, the Isabella isn't much to look at compared with other species, but its immature larva, called the black-ended bear or the woolly bear (and, throughout the South, woolly worm) is one of the few caterpillars most people can identify.
  • Woolly bears do not actually feel much like wool—they are covered with short, stiff bristles of hair.
  • In field guides, they're found among the "bristled" species, which include the all-yellow salt marsh caterpillar and several species in the tiger moth family. Not all are 'woolly bears!'
  • Woolly bears, like other caterpillars, hatch during warm weather from eggs laid by a female moth.
  • Mature woolly bears search for overwintering sites under bark or inside cavities of rocks or logs. (That's why you see so many of them crossing roads and sidewalks in the fall.)
  • When spring arrives, woolly bears spin fuzzy cocoons and transform inside them into full-grown moths.
  • Typically, the bands at the ends of the caterpillar are black, and the one in the middle is brown or orange, giving the woolly bear its distinctive striped appearance.

Do Woolly Bear Caterpillars Forecast Winter Weather?

According to legend, the wider that middle brown section is (i.e., the more brown segments there are), the milder the coming winter will be. Conversely, a narrow brown band is said to predict a harsh winter. But is it true?

  • Between 1948 and 1956, Dr. Curran's average brown-segment counts ranged from 5.3 to 5.6 out of the 13-segment total, meaning that the brown band took up more than a third of the woolly bear's body. As those relatively high numbers suggested, the corresponding winters were milder than average.
  • But Curran was under no scientific illusion: He knew that his data samples were small. Although the experiments popularized and, to some people, legitimized folklore, they were simply an excuse for having fun. Curran, his wife, and their group of friends escaped the city to see the foliage each fall, calling themselves The Original Society of the Friends of the Woolly Bear.
  • Thirty years after the last meeting of Curran's society, the woolly bear brown-segment counts and winter forecasts were resurrected by the nature museum at Bear Mountain State Park. The annual counts have continued, more or less tongue in cheek, since then.
  • For the past 10 years, Banner Elk, North Carolina, has held an annual "Woolly Worm Festival" each October, highlighted by a caterpillar race. Retired mayor Charles Von Canon inspects the champion woolly bear and announces his winter forecast.

Most scientists discount the folklore of woolly bear predictions as just that, folklore. Says Ferguson from his office in Washington, "I've never taken the notion very seriously. You'd have to look at an awful lot of caterpillars in one place over a great many years in order to say there's something to it."

Mike Peters, an entomologist at the University of Massachusetts, doesn't disagree, but he says there could, in fact, be a link between winter severity and the brown band of a woolly bear caterpillar. "There's evidence," he says, "that the number of brown hairs has to do with the age of the caterpillar—in other words, how late it got going in the spring. The [band] does say something about a heavy winter or an early spring. The only thing is . . . it's telling you about the previous year."

What do you think? Do woolly bears predict winter weather? What other signs of the seasons tell us about coming weather?

If you're interested in winter weather predictions, be sure to check out The Old Farmer's Almanac, too!

Related Articles

More Articles:


9-13-2012. Last wknd, I saw

By Zuza

9-13-2012. Last wknd, I saw several Woolies in my back yard. Some were cream colored, some were light-brown/orange, and some were all black. None appeared to have bands. They were hiding in the thick grass between stuff. I was thinking that maybe they get darker as they mature in age. I hope this winter is a bit colder than last though -the bugs are real bad this summer in Chesapeake, VA.

Just found a Wooly bear

By Deb Lee

Just found a Wooly bear caterpillar on the front walk here in mid southern Ontario Canada just outside of Sarnia. All orange. Hopefully that means a mild winter. Don't want a repeat of two years ago when the 402 highway was shut down because of the huge snowfall.

It is Sept. 1st today in the

By Peacefulcreek

It is Sept. 1st today in the Rocky Mtns. of Colorado. Twice in the last week, I have seen the "wooly worms" crawling across my pavement. Both were good sized worms and both were entirely black in color....no brown bands on either of them! If the folk lore remains true, we will be in for a severe winter this year...which is good because we have been so dry from past winters hence our summer of forest fires here in Colorado. I sure hope it is a very snowy cold winter here in the Rockies!

We found many black and

By Jeanne46

We found many black and yellow/orange ones in Austin, NV today. My 4 year old is fascinated by them and wants to see them change into moths. Will they survive in a water jug with holes and cottonwood leaves?

August 27, 2012 and we still

By Chey

August 27, 2012 and we still have not seen one single Wooly worm this year. Last year, we saw many that were almost completely blonde or very light brown and we had an unusally warm winter. This year, we are not seeing ANY anywhere. (southeast Ohio). has anyone else seen any this year?

Mostly, if not all brown here

By salmonid74

Mostly, if not all brown here in Maine

I saw a wooly bear a few days

By rebecca rebecca

I saw a wooly bear a few days ago Aug 25, 2012, it was all black. Just to let you know.

All black ones here in

By Cox

All black ones here in Fairview tn

I have watched them for many

By Anonymous in maine

I have watched them for many years and it holds pretty true, last year 2011 was a wide band and we had a mild winter, I just saw some with no band, hope this is not true of the worst winter ever. Get ready folks

Ours appear to be all black

By AnonymousSherry

Ours appear to be all black with an under shadowing of orange. We will see what this winter brings.

I live in central Wisconsin,

By echo

I live in central Wisconsin, and have seen three Woolly Bear Caterpillers Between April 12th and 15th. They are crawling, look big and fat. How come I am seeing them now? I am a road/walker and see a lot of nature.

Hi, Echo, In northern

By Almanac Staff

Hi, Echo,
In northern climates, there are usually 2 generations of banded woollybear (isabella tiger moth) per year. Overwintering caterpillars emerge around May. They eat a bit and than pupate. Adult moths emerge in early summer. These will then produce another generation that emerges around August. These caterpillars will overwinter, starting the cycle again.
The fall-generation caterpillars are perhaps more noticeable because they are searching for a good place to overwinter, so they travel about more.
In southern areas, there could be three or more generations. Hope this helps!

i love to explore and find

By Addie

i love to explore and find bugs. When i do look for bugs the 1 that i try to look for the most is the Woolly Bear Caterpillars. I love caterpillars so much. I look for them every day and I'm always asking my mom if i can order some but she says NO!!!! I'm in 2 grade and i have a sister that is in 3 grade. I have a mom named Sasha. I have a dad named Andy and i have a dog named Howie he is just a baby!

Not sure if it is the "Woolly

By LisaRenee

Not sure if it is the "Woolly Bear" I've always used to predict the winters in NE Indiana or something different (because I've seen such a wide variety over the years)-- but I always called them "Woolly Worms" . . . My parents always told me simply that the lighter the color the harsher the winter and I'm pretty sure it has always been correct. I remember seeing white ones and then having a very harsh winter. As an adult I don't always see them but this past fall I saw more of a yellow color one . . . so far it has been a realatively mild winter. My prediction was, "It will not be a harsh winter--more of an 'inbetween' winter." Again, I don't know if what I look at is the "Woolly Bear."

I found a Woolley bear under

By Secarpenter

I found a Woolley bear under some of my wood that's piled up all curled up in 27 degree weather on January 18th 2012. I thought it was dead because how cold it is outside but when I brought it inside it eventually opened up and started crawling around everywhere. It's really strange to find an alive one in the middle of the winter. This one has a wide black stripe where it's head is and long brown/orange middle and a short black tip. I live in Radnor Ohio and so far this winter it has been very wet and mild. Maybe 2 inches of snow all winter here so far.

We had an ALL BLACK Woolly

By Becky12345

We had an ALL BLACK Woolly Worm in our driveway over the weekend, in Garner NC. It could mean a COLD Winter!! I put him in safe area under some bushes.

I Found an all black "Woolly

By Kevin Hull

I Found an all black "Woolly Bear Caterpillar" on North Colonial Dr. Cortland, Ohio. I also have three friends in the same area, with one in Champion, Ohio that found all black ones too. As my father, God rest his soul....used to say. It's gonna be a very bad winter. Nov.2,2011.

RE: the number of wooly worms

By gradofan

RE: the number of wooly worms this year - it all depends on where you are. There are almost none in Illinois this year - very odd, indeed! Maybe they've gone the way of the honey bees.

Does the fact that we seem to

By Falltime

Does the fact that we seem to have sooo many woolly bears have anything to do with predicting the weather? I don't remember a time when there has been so many. Dodging them in the road is a challenge!

Here in waaaaayyyy Upstate


Here in waaaaayyyy Upstate New York on Vermont border we are just now seeing Wooley Bears for the first time this year. Alll so far have been even between black front, orange middle, and black rear. The "lore" I have always heard is that the segments predict how long each portion of the winter will be---front section is for Fall and Early winter; middle for mid winter and rear for end of winter shading in to spring. This does correspond with a harsh or mild winter if you think about it just not direct temperatures. Altho we have very few squirrels out here in Farm Country (go figure!) we have a bumper crop of black walnuts on yard trees and have seen LOTS of acorns on trees and ground. Have seen LOTS of foxes recently many more and with more fur than you would expect. More road kills than usual among all furry things---does this mean they are more active looking for food? And baby skunk in the daytime last week! Enjoying introducing very curious grand daughter to Wooley Bears and lady bugs etc but NOT so much the incredibly ANNOYING and prolific "Biting flies" that followed the recent flooding here. What is UP with THAT??????

I just saw a woolly bear ALL

By kimbo96

I just saw a woolly bear ALL ORANGE with just alittle black band around face. What does that mean? I live in upstate NY

I'm upstate as well, in the

By kimmp

I'm upstate as well, in the Finger Lakes area right near Lake Ontario. I have fou d 3 woolys that had a little black on head and tail and a big band of brown/orange. A friend of mine is finding the same. I haven't seen this much brown/orange on one in quite awhile. Livestock don't look too shaggy coated either.

I can only hope it will be mild, as I absolutely hate winter.

Hello, it might have been a

By Almanac Staff

Hello, it might have been a different variety. According ro folkore, the narrower the brown (orangish) band on the woolly bear caterpillar, the more severe the coming winter.

i have seen wooly worms this

By shadowfax667

i have seen wooly worms this year that are almost blond with no red or black bands. any idea what this means? i am in the laurel highlands in western pa

If by "blond" you mean the

By Almanac Staff

If by "blond" you mean the lighter brown section, it means that the wider the middle brown section is (or the more brown segments there are), the milder the coming winter will be. Conversely, a narrow brown band is said to predict a harsh winter.

We are in So. CT near NY

By fuzzwatch

We are in So. CT near NY border and just found a Wolly Worm that is about 50:50 brown and black. What does this mean for CT winter?

We are in southern ct and

By fuzzwatch

We are in southern ct and just found a black and brown caterpillar that was evenly brown and black. What does that mean??

I have also been seeing a lot

By Racing6

I have also been seeing a lot of woolly bears here in central Ohio that are exactly half brown and half black. I am also curious as to what that means.

I found quite a few this year

By starkey

I found quite a few this year that are all brown, one had a small segment on the front that was black. My neighbor also found all brown ones too. I live in Webberville, MI

Here in Toronto Ontario I

By canady

Here in Toronto Ontario I have seen off white and totally gray ones:-) Interesting! Two one the off white and the other one was silver gray.

Stay away from these, the

By Irishmom77

Stay away from these, the bristles are infectious.

All Black here in Salvisa. Ky

By jamescornelius

All Black here in Salvisa. Ky from North Carolina and have always seen striped in NC! I think the solid colors mean a solid winter!!

I agree, all that I have

By Fuzzey23

I agree, all that I have found here in North East Ohio, 2 miles from Lake Erie are also all black. Not boding well for a smooth winter at all.

I live in NE Ohio as well.

By Gent 716

I live in NE Ohio as well. Just returned from a walk in the Metro Parks, saw several of them and they were more than half orange..... Although I was not at the lake but in the Chagrin area, I wonder why the difference in the same general vicinity... Still hoping for a mild winter!!

They are all black here in

By BobL

They are all black here in Springfield Twp, NJ too. Have never seen them all black!

On my way home from work, I

By Jeannie Godfrey

On my way home from work, I have been seeing that wolly worm on the road and it was very black every time I have seen it and I am seeing it more and more. I live in Roughemont NC

The Wooly I saw this week

By AnonymousSherry

The Wooly I saw this week appears to be all black but with a shadowing of rust color beneath the black.I had heard of the Wooly's predictions but had forgotten so now will see if we have a rough winter. We live in Michigans Upper Peninsula.

Fortunately, the woolly bear

By TheElfGuy

Fortunately, the woolly bear caterpillar I had just found late last week was almost entirely reddish-brown, with hardly any black whatsoever. I sure could use a mild winter here in Northern Virginia. Last winter was hellacious, with a three foot snowfall in one weekend last February. I am soooo not looking forward to a repeat of that. Thank you ~ (•8-D

I live in Fayetteville, NC.

By danielle.dixon

I live in Fayetteville, NC. Just saw a wooley worm for the first time! I had to look it up just to know what it was. I was so surprised at how big it was. I took pictures with my finger for comparison :) No brown/red at all. Completely black. It will be interesting to see what the weather is like here!

I live in Western NC about an

By cljackson

I live in Western NC about an hour west of Boone, NC. This year the Woolly Worms here are mostly black with very little red or either all black.

I live in the southwest part

By debmar10

I live in the southwest part of Virginia (the mountains) and I've seen two caterpillars, barely the tinest of black on each end and 99% brown/orange in the middle. Never seen one that wasn't striped at all---interesting to see what kind of winter this will be.

I have seen all black ones

By djmilesway

I have seen all black ones then some with black on each end and brown in the middle. What does that mean?

“If they’re solid black, it’s

By Theresa Upstate

“If they’re solid black, it’s going to be a bad winter. I’m hoping for a bad winter,” said Dick Kilmer of Moscow.

Georgia wolly worms/bears are

By susan@lambsbest.com

Georgia wolly worms/bears are all orange this year as well.

NJ wooly bears are all orange

By fireonered

NJ wooly bears are all orange this year too! I thought I was imagining it, but then I found this article. I wonder what is going on?

Wooly bears, Acorns and ice

By Teddy

Wooly bears, Acorns and ice in the Northeast.

This year there are so many acorns I cant walk a step in the back yard without stepping on three. The wooly bears are all orange though. This combination usually means that when we have precipitation we will see little snow, a lot of ice and the winter will be longer than normal. We are collecting the acorns for the deer due to the ice build up on trees will make it nearly impossible for them to get a decent meal in late february. Signing off in the lower hills of the Berkshires

Here in S.W. Missouri, as far

By nawe417

Here in S.W. Missouri, as far back as when I first came here in 1965, all the old folks predicted the winter as to how black looking they were. When lighter, a mild winter, when dark, a harder winter.

Our wooly worms/bears are all

By jbauer81

Our wooly worms/bears are all orange also! Here in central southern michigan. What does it mean?!

Our woollies have always had

By jjstewart

Our woollies have always had thick dark bands on them. yesterday I saw two without a single band....they were both a dark orange, very furry and quite large. what does this mean for this winter in southern Wisconsin?

I grew up in PA. One year I

By glorioussnookie

I grew up in PA. One year I showed my Mom one I found, she said"Oh No are they all like that?" I told her yes, she said, we're in for a bad winter" Well those wooly bears were right, it was a terrible winter. this past fall in West TN the wooly bears were black and so far we have had 17 inches of snow when a normal total snowfall for the season may be 1 to 2 inches. I have lived here for 14 years and this is the first time I ever saw the wooly bears all black and I would definitely say they were right! So much for science ha!ha! GOD BLESS!

Interesting article -- but

By Ron Ro

Interesting article -- but what does it mean when up here in central New York, neither I nor my family have yet to SEE even one woolly bear this Fall? It's the first time I can recall that happening in my 73 years up here.

As of October, 2012, I've

By Kimmie76

As of October, 2012, I've seen 2 wooly bear caterpillers with NO BLACK. Does anyone know what that means for Catskill Mountain weather this season?

In up state NY (Watertown)

By Theresa Upstate

In up state NY (Watertown) yesterday I saw my first Woolly Bear of the season and it was very black on both ends with an equal amount of rust in the middle. So in three parts two were very black and one deep rust. :)

I just saw my first woolly

By In Carthage, NY (near Theresa)

I just saw my first woolly bear of this season and, believe it or not, it was about a half inch of black on the head and the rest was all brown/orange. Does this mean no winter?????

I also just saw my first

By Enrufo

I also just saw my first woolly bear of the season, in Albany, NY. It had a pretty broad band of brown, maybe 1/2 of its body length, in the middle. Mild winter would be nice.

This is the first time I hear

By Chrysa_1

This is the first time I hear this about the Woolly Bear Caterpillar although I've been seeing them my whole life! Thank you!

I knew of wooly worms in

By Edith Welch

I knew of wooly worms in Nebraska but here in Denver, Colorado I don't find the wooly worms. Do you know what areas the worms do not ive in? and why?

We too were brought up on

By Jill Cowgill

We too were brought up on looking at the wooly bears for how cold the winters would be. We were told that the blacker they were the colder it would be.
Personally, I hope they are wrong, this year's are mostly black. Like most everyone else, the squirrels are very busy collecting this years bumper crop of nuts.

I agree. I have paid

By BethA

I agree. I have paid attention to them all my life, and I am now in my late 40's. It looks like a bad winter this year, the ones I have been seeing are all black with a tail of brown. I am from Northern Indiana, so I can't wait to see them prove itself right as a predictor once again.

I do believe in the woolly

By young gal from Ohio

I do believe in the woolly bears prediction of who winter will be. I have lived in Ohio for 10 yrs now. I heard this when I first moved here. I was like,,, what that's crazy.. But they did seem to let us know and they were correct just about every yr. Crazy but thankful to be ready for a harsh winter. I grew up in Maine. We have BAD winters up there. So this was very interesting. So to end this note.. I seen 4 this week and they are all Black.. with just a little rust brown by the head and on its tail.. and we have had much colder weather for this time of yr already.. not much of a fall weather.

well Hope you have a safe winter and Stay WARM :0)

Jackson Center, Ohio

Interesting that we are

By crystalball

Interesting that we are getting such a disparity in colors of wooly bears in Ohio. I was out walking just minutes ago and saw four with very wide brown centers with just a bit of black at each end. This would indicate a mild winter based on wooly bear lore.

I believe in the woolly bear.

By rayah

I believe in the woolly bear. I have seen several in my area this year, and the squirrels has been very busy this fall. I'm looking for a long cold winter this year in East Central Kentucky.

Very interesting and

By adirondack13424

Very interesting and informative article. A friend of mine recently told me squirrels were very active this past summer gathering all the nuts they could, which he said they do for in preparation for a long harsh winter. I hope he's wrong!

I was raised on this way of

By kentuckywoman54

I was raised on this way of forecasting the winters. The woolys here in my part of Ky. are showing very little brown. Very large area of black on both ends. Will be interesting to note what kind of winter we end up with. Unusually cold for this time of year and early frost so far...

I live in N.E. Ohio just east

By wolley nut

I live in N.E. Ohio just east of Cleveland and the wolly bears I'm finding are almost all brown with only the very tips on each end black. This would indicate a warm winter here. I hope they are right.

I live in this area of Ohio

By Chyk

I live in this area of Ohio too and the Woolies we've seen have a large brown middle with just the ends being black. Just like last year! My bet is on the Woolie and we are having a mild winter (so I hope!)

I live in the same part of

By buck hunter

I live in the same part of Ohio I've been out archery hunting for the past few weeks and seen dozens off woolly bears with little to no brown stripe and the buck I got Monday over I'm pa had more fat on real it then pony deer I've ever got I would say we are going to have one real bad winter

I have also heard this all my

By Tigress

I have also heard this all my life and I agree has been accurate to a point. My belief is old sayings from generation to generation have thier reasons to carry on, If they did not believe in knowing what they see to be the truth, which is to predict the coming winter. Good feeling to read this article.
Thank you

i have heard as a child for

By awtup6h

i have heard as a child for weather forcasting the catapiller is quite accurate in priducting the coming winter

This is something I've heard

By Craig King

This is something I've heard all my life, passed down from several generations in my family. I never made the empirical observation myself, but my grandmother did every year, and she swore by it! Some other signs she looked for were the thickness of hulls on hickory nuts and walnuts, and if the garden produced a bountiful crop that summer.

I have to agree some with

By Howard Kruse

I have to agree some with Craig King. I have watched the Wolly Worm for years but have not gotten any answers about the weather. I find the the Quantity of Nuts and wild berries that are produced, the thickness of the shells are a better clue as to the temperature of the winter. Also find that the closer to the ground that the wasps and hornets build their nests in the summer the colder it will be in the winter. I think that folks in different areas have their own special ways of determining how they think the weather is forecasted in that area.

In MN, we know we are in for

By Edgar Toensing

In MN, we know we are in for a long winter when the highway crews are putting up snow fences in Aug.

hmmm very cool and my

By krenaudsmith

hmmm very cool and my daughter was facinated when i read it to her

Very interesting. Thanks for

By howea0725

Very interesting. Thanks for the good read & keep on predicting!

Post new comment

Before posting, please review all comments. Due to the volume of questions, Almanac editors can respond only occasionally, as time allows. We also welcome tips from our wonderful Almanac community!

The content of this field is kept private and will not be shown publicly.
By submitting this form, you accept the Mollom privacy policy.