physics for beekeepers

Hive temperature and humidity: see how they relate

A graph of how internal hive temperature fluctuated with outside air temperature. Bill Reynolds

A Minnesota beekeeper measured the relationship of temperature and humidity in his hives. In a surprising discovery, he found hive temperature spiked after beekeeper interference.

Inside: See how hive temperature varied with outdoor temperature and humidity in experimental Minnesota hives.

Monitoring hives with a desktop weather station

Back in November, Bill Reynolds of Viking, Minnesota began monitoring the inside of his beehives for temperature. He purchased an inexpensive desktop weather forecasting station with three remote wireless sensors for his project, and he used a fourth sensor to monitor the ambient outside air. You can find the data for the first weeks in the post, “How do honey bees keep their hive warm?

Originally, Bill set up three hives, each with three deeps and a quilt box. One hive contained a colony of Carniolans, one a colony of mutts, and one was empty. He didn’t wrap the hives but placed all three on the south side of a house with a straw-bale wall blocking the northwest winds.

On November 22, Bill wrapped the second hive—the one containing the mutts—with 15-pound tarpaper. Then on November 28, he added a humidity sensor to both occupied hives and began to record the humidity and temperature in each. Roughly one month later, on December 24, he removed the tarpaper wrap from Hive #2.:

4 observations about the monitored hives

Below are some observations Bill made about the experiment, followed by the actual data:

  • When comparing the data from the two occupied hives, the tarpaper wrap didn’t have much of an effect.

  • When wrapping and unwrapping, the temperature spiked inside Hive #2. Presumably, this spike was caused by increased bee activity due to human disturbance. Bill writes, “I am surprised that such little interference outside would cause such a large effect inside.”

  • The outside humidity levels were very high, at one point 99%, but there was no snow. As the outside humidity rose and fell, the internal humidity of Hive #2 followed closely, as did the readings from the empty hive. On the other hand, the humidity of Hive #1 fluctuated much less.

  • Coincidentally, the outside humidity dropped just after the wrap was removed.

Graph of internal vs external hive temperature

The first graph below goes back to November 1 and continues through December 26. It is easy to see that in the occupied hives, the internal temperature fluctuated with the outside temperature (black bars) but was consistently warmer. The empty hive temperature remained consistent with the outside air. As mentioned above, the temperature of Hive #2 (blue) spiked when the tarpaper wrap was added and again when it was removed.

Bill-Reynolds-dectemp_27_14
Bill’s graph of how internal hive temperature fluctuated with outside air temperature.

Graph of temperature and humidity, both inside and out

The second graph shows both temperature (dotted lines) and humidity (solid lines). The outside humidity (green line) fluctuates with outside temperature (black bars). For the most part, the Hive #2 humidity (magenta) followed the outside humidity (green), but Hive #1 (blue) was drier on the humid days and wetter on the dry days than the outside. In other words, have Hive #1 was able to minimize humidity fluctuations.

Bill-Reynolds-jan_humidity_2015
Bill’s graph of hive temperature vs hive humidity in Viking, Minnesota

Direct your questions to Bill

If you have questions, please leave a comment and I will let Bill answer them for you. In the meantime, Bill, thanks so much for this fascinating peek inside your hives.

You can purchase the ambient weather station here: *Ambient Weather WS-10 Wireless Indoor/Outdoor 8-Channel Thermo-Hygrometer with Three Remote Sensors

Rusty
Honey Bee Suite

*This post contains an affiliate link.

About Me

I backed my love of bee science with a bachelor’s degree in Agronomic Crops and a master’s in Environmental Studies. I write extensively about bees, including a current column in American Bee Journal and past columns in Two Million Blossoms and Bee Craft. I’ve endured multiple courses in melittology and made extensive identifications of North American bees for iNaturalist and other organizations. My master beekeeper certificate issued from U Montana. I’m also an English nerd. More here.


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17 Comments

  • On Long Island, NY the weather has been relatively warm. The humidity inside the hive was high with water vapor inside the inner cover.

    I took off the tar paper and opened all the entrances to full open for ventilation. Christmas day it was in the 60’s and the bees were out. Today it was 57. Next week its going to be cold, below 30 and then I will reduce the entrances.

    I keep a reading of the inside temp and one box is very warm. That hive is full of bees and the temperature changes are confusing them.

    Sometimes its best to let them handle the hive naturally instead of micro managing.

  • Very interesting. In Dennis Murrel’s experiments with winter moisture and condensation he stated noticing a big difference between strong and weak hives. Was there any difference in strength between the two hives?

    It’s not uncommon here for people to wrap in tar paper. It’s not for insulation, it’s intended to allow for solar heat gains on sunny days, where another degree or two might allow the cluster to move to a new area of honey in the hive. It might provide the most benefit on sunny days in say February when the days are a little longer and the cluster might be depleting the honey on one side of the hive.

  • Bill writes, “I am surprised that such little interference outside would cause such a large effect inside.”

    Bill’s observations match with mine. When it’s too cold to look inside my hives, I push my ear to the side of each hive to see if I can hear the bees buzzing. If I don’t here anything, I knock on the side of the hive and give another listen and usually hear the roar of the cluster for a few seconds and then I know they’re okay. But some colonies, even with my little “Are you okay?” tap, will wake up in a bad mood and send hundreds of bees pouring out the hive, even when it’s freezing outside. I had no idea it would take the bees so long to calm down, though. The temperature in Bill’s hive seemed to spike for about two weeks after being disturbed. I realize we’re looking at a limited data set here, but these are interesting observations. Perhaps I should invest in a stethoscope or just stop knocking on my hives in the winter.

    I’m curious what kind of readings Bill would get from a hive that’s wrapped all winter and one that isn’t. I’m not convinced wrapping does my bees any good because my hives are in a very wet, damp, humid environment. The wrap is soaked most of the time and even turns to ice from time to time.

    • Phillip,

      I’m convinced wrapping only helps if there is lots of sun (i.e. lots of solar heat to collect), otherwise moisture seems to be a bigger problem with wrap than without it.

  • From the looks of the second graph, I’d say your carnies are doing better than the mutts when it comes to temp and humidity control. Glad to hear it, as I have carnies, and live in the Pacific NW, where humidity can be high all rainy winter long! Still can’t tell if they’ll make it through this winter though, we had honey robbing in the fall :(. And it’s been too cold to get in the hives to check/replace candy boards. Beekeeping, not for the faint of heart!!
    -E

  • Hi Rusty and Bill, these are really impressive charts. Rusty can you ask Bill to email me at ostrofsky[at]pacinfo[dot]com? I hope to get jpg versions of the charts. This way I could enlarge them so I can better read them. I would like to show them in my beekeeping classes illustrating the effect of disturbing the colony. Finally, I would like to find out where to purchase the equipment. Thank you, Morris

  • That is really interesting. So basically, the bees in this test were better able to regulate humidity inside the hive that wasn’t wrapped. It would be really interesting to test this on a much larger scale. It makes me kind of glad I didn’t wrap mine this year but put up a wind block instead.

  • I am surprised by the statement that “When comparing the data from the two occupied hives, the tarpaper wrap didn’t have much of an effect.” Before wrapping the two hives were at almost the same temps, but after wrapping the blue line was consistently above the green line, with only a few exceptions (perhaps on overcast days with no solar gain??). Of course, replicates are needed but I would have thought that the wrapping has a reliable effect of helping to maintain slightly higher temps.

  • Morning

    Roger – Prior to wrapping Hive 2 (H2), its temp ran about 3-4 degrees colder than Hive 1 (H1). The best I could tell, both clusters were mostly in the bottom deep. After wrapping, for about 24 hours there was a spike in temp for H2 of 10 degrees. Once the spike settled, H2 ran about 6 degrees warmer than H1. So in all, there was a shift of about 10 degrees.

    Before removal of the wrap both hives temperatures were within a degree or two. Upon removal of the wrap a 6 degree spike was noticed in H2 for about 24 hours. After the spike settled, the temps between the two hives was again only a few degrees.

    So, a few degrees here and there was the reason for the comment “When comparing the data from the two hives, the tar paper wrap didn’t have much of an effect”.

    Thanks for the comment and reading the blog!

  • This is all extremely useful.
    I’m in a very different climate – my issue is at times the heat.
    Where would I be able to order the equipment?

    thanks max ( Queensland, Australia)

    • Max,

      There is a link to the equipment at the end of the post (above) but I don’t know how that would work from Australia.

  • Very interesting study. I love REAL data; thank you for including the graphs. Rusty, I think it would be useful to replace them with a higher resolution because it IS difficult to see details such as the key. The text states the colors so the trends are evident, but nerdy folks like me are interesting in all of the details.

    Two questions: 1) I am wondering how and where you put the sensors in the hives? 2) I use monitors for my chicken coop but after about a year the connections rusted in the remote. I am able to just a new remote and the system remains useful. I was just wondering if you had the same problem as me?

    (Rusty, thanks for a super useful site! It is one of my GO-TO websites anytime I have a question.)

    • Amy,

      I can only post what I was given, so I can’t change the resolution. Generally, temperature and humidity sensors are placed just above the uppermost brood box. Some sensors, like the Broodminder, are designed to withstand conditions in the hive.

  • This is a site that Broodminder uploads to. It is a public site and might find it interesting to view areas around where their colonies are located. They even have areas outside the U.S. I have just put them in my 5 hives in December. I wish that I had bought the ones with humidity also, but find the monitoring of temperature very helpful. I saw one of my colonies had moved to the upper brood box and was able to remove the bottom brood box, that was in need of repair on a 60 degree day. I will be looking into the desktop sensors for humidity, that was shared on this site. Thank you so much for your wisdom you share. Sarah

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