What happens to honeybees in the winter?

It’s snowing, and I figure that’s good, for the bees: they slow down, go into cluster, don’t consume as much food, and the queen stops laying.  There’s no food here for bees from mid-October to February, so there’s no use in the bees looking for any.

Around this time of year, I’m often asked: what happens to the bees in winter, do they go to sleep?  No, they don’t but it’s a good guess; we are in an area where many animals go into hibernation in the winter.

What honeybees do is even more fascinating than hibernation.  A strong, healthy hive will form a cluster.  This is basically a ball of bees that covers a number of frames and usually centers itself in the vertical center of the hive.  The size of that ball will depend on how many bees are in the hive and what the temperatures are outside the hive.  (At the end of this piece, there’s a temperature / “what’s happening” chart).

Before I launch into this, I’ll be using are two sets of numbers (besides Fahrenheit, F, and Celsius, C).  There is the temperature of the bee cluster and the temperature outside the cluster.  The bees only heat the cluster; the rest of the hive is the same temperature as the bee yard.

The bees need to keep the cluster’s core between 93 and 96 Fahrenheit (around 35 Celsius). The very lowest the cluster’s center can drop to is 55F (13C). Lower than this and you have a dead hive.  Different sources offer different exact temperatures, but they are all in the same ballpark. The numbers here are drawn from internet searches, and from “The Biology of The Honey Bee”, by Mark L. Winston (a fabulous book and fun to read).

Around here winter temperatures can drop to 20 F (-6 C). That is warm compared to some beekeeping areas, so how do the bees manage to keep the heart of their cluster between 40F (4C) and 95F (35C)?

When temperatures outside the hive drop to about 64 F (18 C) the bees start form their cluster (that ball of bees).  An outer shell of bees line up side-by-side, facing into the cluster to create a thermal barrier. At this point, the body heat of the outer layer of bees supplies enough warmth to maintain the bees inside the cluster.  This outer layer of bees can be one bee-layer thick, or can build up to a number of bee-layers in thickness.

The bees on the inside can still walk around over the comb and sometimes eat a little honey.  Periodically bees switch places, with ones from the inner core taking up a position on the outer core to allow the outer bees to go “inside”.

Just like there’s a minimum temperature for the heart of the cluster, 55F (8C), the outer shell has a minimum temperature: 46F (8C).  If the outer shell drops below this temperature, the bees can no longer move their flight muscles. (Remember this is their temperature, not the beeyard temperature.) If the outer shell drops below 46F (8C) the bees will fall off the cluster, and die.

Here’s what happens when the temperatures in the bee yard start to drop:

Bees will begin to cluster when the temperature is about 65F (18C).

When the thermometer drops to 57F (18C) that cluster becomes a compact shell of motionless bees.  At this point the body heat of the bees lined up side-by-side on the outer shell generates enough heat to keep the colony warm.  Remember, this layer can be many bee-layers deep.

At 41F (5C) the cluster can still be quite large, and can cover 8 to ten frames.

As temperatures plummet  from around 41F (5C) to 23F (-5C) the cluster begins to contract.  When the outer temperatures hit 23F (-5C) the outer shell of bees will start to flex their thorax muscles.  These are attached to the wings, but the wings don’t move, just the muscles.  This generates heat rather like human isometric exercises (or like me when I get in my pick-up on a freezing day and the heater has not yet kicked in).

If it keeps getting colder, the cluster will keep contracting. At 28F (-2C) the cluster may cover 6-8 frames. 7F (-14C) it can get down to 4-6 frames. At -15F (-26 C) they tend to jam themselves onto two frames.

This contraction explains why in a really cold winter, or when over-wintering hives with small populations, the bees can die surrounded by honey.  They simply cannot leave their cluster to go get the honey.

As supplies dwindle where the cluster has formed, the bees will move up.  They seldom move to the sides.  After all, going up between the frames is far less work than moving the ball of bees around all the frames.

I have heard that beekeepers have suggested drilling holes into the middle of frames to allow bees to move more easily around and through their clusters.  This makes sense, but I’ve yet to meet anyone who has tried it.

There are times when I need to over winter a nucleus hive.  I start these throughout the year so that I always have a viable queen in case one fails in a stronger hive, or, if they do well; I’ve a new hive in the making.  This means I often have nucs as winter approaches.  The number of bees in a nuc is not sustainable in our winters here.

My solution has been to load the nucs with honey and put them on top of a strong hive.  They are separated from the lower hive by a cover/bottom board piece (one could use a simple piece of wood).  This gives them total separation from the lower hive, with the benefits of subfloor heating.  Something I wish I had here right now.  Yes, it’s still snowing, and I don’t “do” cold.

Here’s an easy to read beehive winter temperature chart:

Optimum Core Temperature : 95F (35C)

Minimum inner cluster : 55F (13C)

Minimum cluster shell : 46F (8C)

Bee Yard Temperatures and Bee Results:

64F  18C            bees begin to cluster

57F  14 C           cluster exterior becomes compact shell.  The bees are motionless in the outer                                shell, but still moving  around inside cluster.  This shell can be many beelayers                              thick

41F    5 C            Cluster can cover 8-10 frames

23F   -5 C            Outer shell of bees starts moving their muscles to generate heat

28F   -2C            Cluster can cover 8 -9 frames

7F    -14 C            Cluster can cover 5-6 frames

15F  -26 C            Cluster may only cover 2-3 frames.

Want to read more about it?  Check out The Biology of the Honey Bee, Mark L. Winston. You can download it, buy it, or find it at your local library.

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Brookfield Farm, a small off-grid apiary in Maple Falls, WA focuses on the beauty and bounties of Washington’s wilderness. We sell honey from our bees, whose chemical-free, antibiotic-free hives are home to bees who fly Washington’s mountains. Herbal salves and lip balms from Brookfield beeswax. Delicately infused honeys and vinegars. Varietal honeys from independent Washington beekeepers. Handcrafted wooden furniture. Handcrafted wooden furniture based on designs that have been proven over centuries. Award-winning DVDs that take the viewer up the Pacific Crest Trail and through Mount Baker’s wonderful wilderness. Handcrafted wooden furniture based on designs that have been proven over centuries. Karen Edmundson Bean: beekeeper, photographer. Her love of the wilderness inspires her to discover new ways of bringing the wonders of nature to others. Brookfield Farm : the tastes, textures, sounds, and images of nature.
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22 Responses to What happens to honeybees in the winter?

  1. eric hawbaker says:

    Wow. This is exactly the information i was looking for! Thanks for the great writeup and all the detailed info. Bees are my favorite animal because 1. They are so interesting 2. Honey! 3. They look really cool! I wear black and yellow stripes a lot because it is cool. It would be great if you could add some pictures or video of this. Also can you write up something like this about how bees fight? They are small but really tough and they only have a one time use weapon! Always have their backs againstthe wall. Thanks!

    • Hi Eric, Thank you for your nice comments. I too think bees are totally cool. It would be interesting if someone did insert a mico camera into a hive to record images. I don’t have that technology. Thank you for the idea about flight – when bee season rolls to an end and I’m searching for something to write about in the winter – I do believe I’ll use your idea. Thanks again

  2. kerry says:

    Hi – have stumbled across your site whilst looking for some information, so maybe you could help?! We have bees living inbetween our outter and inner wall – outside our bedroom. There is a crack in one of the outer tiles and you can see the bees flying in and out. I know bees are protected but this is driving us to distraction as the noise is keeping us awake and it means we can’t open our windows. I was hoping that come the winter they would leave and we could block the hole up, but are they likely to stay there all winter aswell? Many Thanks

    • Hi Kerry, I don’t know where you are located but first two points: 1) You must get these bees out of your house. Even if they leave of their own volition, they will leave behind wax, honey, possibly brood – all of which will harm your house. 2) it is illegal in most places (as it should be) to kill honeybees.

      What to do: You (or someone else) must remove the bees by either a) setting a bait hive and drawing them out or b) just opening the wall and removing them and their hive. If you do “a” (draw them out) you still have to open the wall and remove the hive.

      Who will do this: Go on line and do a search for your local “bee club” or “bee association” or “swarm catchers” the clubs and associations usually have a list of “swarm catchers”. But be clear, as you have done here, that you have bees inside a wall. They will often have a person, or know some one who will do a “cut out” – cut the bees and hives out of your wall.

      Then what: you get to repair your own wall.

      In the future: try to use 1/8th inch hardware cloth to close off any bee sized openings (opening greater than 1/8th inch) in your home. I know, what a pain.

      On the positive side, the bees are doing well in your area (not a lot of compensation, I know…)
      Good luck

  3. Sean says:

    Thanks for the info.
    Just to let you know your positive temperature conversions between F and C are correct; however, your below 32F/negative Celsius temperatures are off considerably. Given that this is important to the content of the message, I felt it important to let you know. For example: 15F is -9.4C (you listed -26C which would actually be -14.8F nearly 47 degrees below the freezing temperature of water).

    Conversions:
    Celsius to farenheit multiply by 1.8 and add 32 e.g. 10C is 50F (10×1.8=18+32=50)
    Farenheit to Celsius: subtract 32 then divide by 1.8 e.g. 50F is 10C
    (50-32=18/1.8=10

  4. Pingback: What happens to honeybees in the winter? | CCBeekeepers

  5. Shawn says:

    Would it be all right to put hey around the Hive to keep bees warm would that be safe

    • A lot of people do it, but if you do, I’d suggest very strong mouse guards and/or that you put out some mouse traps or show the cats the way to the hive. In my world hay is an invitation for mice. Then the mice see the nice hive. I wouldn’t do it. But as I said, it works for a lot of people

  6. kate fothergill says:

    Hi, Im probably clutching at straws here but I found a huge fluffy bee on my patio today. I assumed it was dead and picked it up. then I saw it moving its legs, I took it in to my home and it perked up. I’d read that sugar and water solution my help. I out some near and it fell in to it. So I picked it out and let it dry out. Its now in my airing cupboard in a container (with the lid off) what should I do with it. it’s huge and looks so pretty?

    • Well, you’re probably clutching at a dying bumblebee (large, mainly black, with maybe some red or yellow, fluffy) – the bumbles die each winter. The young, who were laid in the summer, will emerge in the spring. So you’re probably only postponing the inevitable. But if she stirs, and the weather is not ice-cold, you should release her. Bear in mind that Bumbles, unlike honeybees, sting repeatedly (not just once). Nice of you to try, but remember the nature of nature is change, including both birth and death.

      • kate fothergill says:

        Thank you for the reply, She did perk up when I brought her in but I noticed she had some little mites on her so I put her back outside, on the patio where I found her, then a seagull ate her up. A bit graphic but, as you say, it’s just nature.
        Thank you for the information though. Its very interesting.

  7. joe says:

    Thank you for your detailed info, i have found this to be not only very interesting but helpful to me. Eary oct. I was given 2 frames of italian honeybees that were the remnants of a hive that was destroyed by yellowjackets. I had a queen shipped to me, bought a nuc box and made a hive heater with 25 wat red bulbs and a wireless outsibe thermometer and a dimmer for control. I live in northern ohio and tonight will be down to 5f. Wish me luck, as I have only one frame of honey stores and am currently feeding fresh beesugar syrup . Thanks for the info as i am desparately trying to save these bees.

    • Good idea on the heater, they’re going to need heat – but they’ll also need food. I’d suggest you try fondant (bee candy) I’ve got a recipe with an update (I hope) from Bingaling Bees – Brad’s got a really good receip, so if I don’t have it google Bingaling in Mt. Vernon, WA for his fondant recipe – It’s hard for the bees to dryout the syrup when they’re cold, so the hard candy is often better. You’ve got a challenge there, but heck, that’s what beekeepings about : the challenges…

      • joe says:

        Call this a challenge……Thanx for your insight, i find myself to reread any points that i come accross in terms of bee advice many times in my past. I am not real good with keeping bees, for lack of experience, hence i will pick up on simple logic quite fast though…i have picked up on some things already in this blog ( such as bees really dont flap their wings to get warm,just their thorax muscles, that is the first time that i heard that, i always was told it was their flapping wings which didnt sound right to me). Another thing i have heard many times is that bees form a ball to keep warm,seems not logical to me as there simply isnt the room between frames, is this ball encorporating with frames berween the ball?
        Ok my fonant experience….i thought about that first….before the temps fell this fall i had made 4 rock candy frames with beesugar ( which isnt processed as far as for human consumtion, but that is good because some of my research says that beesugar has a PH level closer to natural honey than human sugar does ) my beesupply place sells this sugar.
        I made the no cook receipe (3c water : 16 lbs sugar) X 2, stirred, framed, and dried till rock hard in about 3 days. Tested a week for storage effects in my garage near the concrete,because it holds temps and moisture longer that the abient air around it,acting as the worst case senerio i thouht before i hived them. That lasted 2 days before the candy took on moisture and began to run off the frames. So i stripped them, cooked the sugar to another reciepe @ 270 deg.s for 20 mins. and redid the same, same outcome…so
        it was then i thought about fresh syrup!!!!!!!!!!!!!!!!!!!!!!! location of syrup supply would have to be important, because this would have to be refilled to prevent any molding, a controlable heat source would have to be used and a way to read the effects of heat adjustments.
        So there you have it….i am using fresh syrup, that is not meant to be stored, am using a 1/2 gal pale w/ lid and a piece of stainless screen 1″ dia. molded in the middle, the liquid is held from running out by its own suction. The light bulbs are on each side of this pale in the top nuc box, which has a bridge on the bottom that the pale sits on with a hole cut out just like a hive top feeder, next to the bridge is 2 spaces on each side of the pale that lead to the lower nucbox about 8″, which i have screened in so the bees can warm from the bulbs but, cant move up into the top box when refilling the pale, or get too close to the red bulbs, I am quik at refilling and do watch temps drop. I try to compensate the sudden loss of temp with more heat, try to keep the hive at around 45-47 deg. Do you think thats too warm? 2″ of insulation outside the hive helps alot for the temps to remain stable inside for swinging temps outside day and night. I have wired a 110 v recepticle to a dimmer switch, one plug the cord runs outside to the nuc box , the other side of the receticle i have an exact red lightbulb as the ones in the hive which is also being dimmed, this bulb , I measure the surface temps. with a pyrometer (a gun to measure surface engine temps on your car with) i kind of guess with adjustments buts its close. My electric company has power surges and this sometimes changes dimmer settings, i never thought of that! This has been my little project so far.
        I thought about honeywater instead of syrup,would that be good? Would have to mix thin for that to pass though the palescreen. Any advice that I could use? Anyone have anything to say? Comments all welcome. Thanx. -Joe.

        I am writing to reciprcate my experience, in some detail….because hopefully someone will find insight from my postings or get some ideas for themselves here.

        • Oh, lots of points:
          Clusters: It’s kind of a squished ball in the center, but if there is enough bees, the next frames over will have another “squished ball” – think a ball cut by the frames. This is why some folks with deeps punch holes in the frames to let the bees move between the areas easier (at least this is what I read)
          Fresh syrup : not too good of an idea around here, or anywhere where it’s cold in the winter. The problem is that the bees need to dry it before they can eat it – so if they’re in cluster they can’t really dry it out (which they do by fanning it), so what happens is that you’re introducing water to the hive – the water in the syrup. Candy boards are the best – search my blog for fondant or bee candy, or google BingALingBees.com He’s got a great recipie (mine is crumbly – I think I let it cool too fast – I’m not a good cook)
          The warm hive: I’ll be interested to see how the heated hive works out – Just make sure you have good ventillation – the bees will be breathing, there is moisture in the hive and all that has to get out – so a 1/8″ crack at the front is often used (I drill holes for an upper entrance), you can shim up the top for 1/8 crack – but do give ventilation (cold really doesn’t kill bees, but wet does & wet and cold are really deadly.

  8. joe says:

    Candy Frames….i know in the fall alot of keepers feed, wondering if their bees have enough stores overwinter, i have been online looking for full frames of honey for my bees, cant find these…why? I do find candy frames for sale though, and they are about $30 ea. I have made them also, they are heavy 36 lbs. for 4 frames…..in making them i used 1/2 “hardware fabric” which is just metal screen. If youd like to use ganulated cane sugar,like Dominoes brand, take some screendoor screen staple it on each side of empty frame without the combboard in the middle. Dont screen in 2 inches from thr top and fill full of sugarcubes,why doesnt anyone sell empty screened frame you could fill yourself, someone could make a good buck here, if you do please send me one for using my idea ok.

    • I know no one who would sell full frames of honey – and it’s a bit dangerous for your bees – they can pick up diseases from the honey…you can even move diseases between your own bees by moving frames (I move frames all the time, but I wouldn’t use another beekeepers honey – even my friends….)
      Interesting the candy frames – I like it even better than candy boards… let me know how they work out, and thanks for sharing how to make them.

      • joe says:

        Last sunday here was 50F, moving fast i had some leftover hardware fabric, which is really 1/2 sq. wire mess bought at home depot. I rough cut it to the width of the empty frame with the backing removed, I layed the netting on one side of the frame , and with a household ordinary stapler I stapled the netting to the outside wood edges of the frame, then wrapped the netting under the bottom wood edge and back up the other side. I trimmed the excess netting even with the top o frame edge. Before I stapled this side to the wood, I poured 3 boxes of domino sugar cubes in, fanned them out kinda even, then finished with the stapler. This turned out really great, better,quicker and at 1/5 of the price of a candy frame. The sugar cubes are a tad bigger than 1/2 sq.s, so they dont fall out, and with little work can be reused next year too. You need to try this…..I put 2 frames in my girlfriends hive, I ve yet to do mine.
        Thanx for your imput here, hope you find value in the sugarcube frames.
        I do have a question…..currently I am feeding my bees fresh sugar syrup, mixed this 3:1 sugar. I have only 1 frame of honey stores also, in a 5 frame nuc box x 2 high…I thought about the bee fanning situation hence the thick mixture, do you think I am going to run into moisture trouble this winter?….in prepping my hive this fall I added 1/2″ hole in the top box also, I ve been keeping the heat about 50-55 .

  9. Pingback: Surviving Winter, in a Hive |

  10. jeff says:

    I live in Minnesota and there is a large bee hive/nest attached to the outside of our house, how can I remove this without getting stung or hurting the hive/bee’s? It is January and below 32 degrees. Thanks

    • Are you sure it’s bees and not wasps? If so, then I would call or email your local beekeepers association(s) and ask for their swarm list. I don’t know where you are but : http://www.mnbeekeepers.com/,nemnbeekeepers.org,www.semnba.org,and http://www.tricountybeekeepers.com all turned up on google via “Minnesota beekeepers association”. The Swarm Catchers will come out an retrieve them. Alternately, you can go out and get them by gently brushing them into a box – you could use a soft, wide, light colored paintbrush, and then close the lid, but then you’ve got the problem of what to do with them (and to the possible stings you now have). What an unusual situation to have a swarm in winter. Best to contact the local swarm catchers. Hope that helps.

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