Keeping Bees Cool

Bees inside their hive

Bees are great at climate control. They keep the hive at a constant temperature of about 35 C (95 F) day and night. When it’s cold outside, they huddle together around the brood and shiver their muscles to generate heat. When it’s hot, the bees collect water then position themselves in and on their hive beating their wings to create a natural air conditioning system. They’ll kick any surplus bees out of the hive to reduce the number of hot bodies and increase airflow.

I took a photo of my bees when it was 34 C and they were starting to group on the outside of the hive. Only when I downloaded the photos to my laptop did I notice all the bees pointed the same direction. The 2nd hive is identical. This can’t be a coincidence; this is their air conditioning system at work!

Bees fanning a hive on a hot day – they’re all pointed in the same direction

I don’t have to worry about helping my bees survive the cold, in Sydney the winters are pretty mild (we don’t even get frost on our lawn), but I do worry a little bit about the heat. I’ve read that bees die at temperatures over 48 C (118 F) which is warmer than it gets here but 50,000 bees all living in a couple of small boxes generate a lot of heat. And a flying bee gets a lot warmer than the ambient air temp. Think of a woman, running at a sprint, carrying a 50 kilo bag of sugar strapped to her back in 40 degree heat. When she gets home the house is 45 degrees because all her relatives are over and someone left the oven on high all day. Oh dear. Really, it’s all too much so bees ratchet down their flying (and nectar/pollen collection) when it gets to about 35 and just hang out near the hive, hopefully in the shade.

Bee larvae in comb

That’s lost productivity and there’s not much a beekeeper can do about it (nor should they). But there’s potentially something not nice going on in a hot bee hive that beekeepers should worry about. Beeswax melts at about 62 C (144 F). Since all the bees would have died long before that point, a true melt isn’t really an issue. But somewhere well shy of 62 C, wax gets soft. Wax loaded with honey (which gets very fluid as it warms up) starts to sag. I’ve read about beekeepers finding honey literally running out of the bottom of a hive. Now this is NOT a good thing. Bees can drown. The air flow system will go awry. Eventually the brood can get too hot and all the eggs and larvae die (they don’t do well over 36 C). This is a huge setback for a colony and can cost a hive a generation of workers.

Obviously it’s a good idea to try to keep hives from overheating. Since it’s kind of hard to put a giant refrigerator around a hive, the options for a beekeeper are limited. They include:

Keep a ready supply of water near the hive. This is a requirement no matter what the temp is but becomes paramount when it’s hot. A colony of bees can collect half a litre of water on a warm day to air condition their hive. They need to be able to drink without drowning so there should be pebbles, sand or stones for them to stand on. We have a birdbath with chunks of stone standing in it which the bees use – the water level lowers noticeably faster now that we have bees. When it gets above 30 C the bees run to collect water in droves.

Frangipani shading the bee hives

Providing shade. If the hives aren’t in a shady spot, shade cloth can be erected on warm days. My hives are under a deciduous tree (a Frangipani) and get shade most of the day during the summer so I’m okay here. When it hit 42 C (108 F) yesterday, I did string up a sheet hanging from the branches of the Frangipani to shade the side of the hive from the afternoon sun, but that’s not a normal requirement.

Replace the hive bottom board with mesh. This increases airflow which makes it easier for the bees to stay cool. Since our bottom board is nailed to the brood box (something we plan to fix once we’ve cleaned up all the foundationless comb in the brood box) this isn’t really an option.

Remove a frame from each super. This is meant to improve airflow in the summer. As my hives are in the shade I’d only go for this if a really long heat wave was forecast (40s for a week – which almost never happens).

Provide a water mister over the hives. We purchased a mister to help keep the chickens cool on hot days. Then we thought it might be needed by the bees (the chickens often hang out by the beehives allowing us to kill 2 birds with one stone, so to speak). The water droplets are minute so I don’t think they deter the bees from leaving the hive. We set it up yesterday morning when the temp reached 35 C (95 F); it didn’t make much (if any) difference. It was quite windy and the mist went up and over the neighbours fence which was part of the problem. Also, I just don’t think there was enough water. We put a garden sprayer on the ground in front of the hives (not so close that the water hit the hives) when the temp reached 40 C (104 F) and then we got a drop at the hives to 32 C. It ended up making more than 10 degrees difference. Lesson Learned: Wet the ground well on a hot day before using the misters – they work but a kick start is needed.

Water mister operating over beehives

Yesterday was ghastly. The predicted 42 C (108 F) arrived (fine time for the weather guy to be right) and it was hot hot hot out there until well after midnight (when it was still 35). I think we did a good turn by the bees with the mister but maybe not so much by the chickens. They did wander to the shady bed near the bees and the mister but didn’t hang out there. They were just too hot to settle anywhere. They lifted their wings and panted and it was pretty sad to watch. I kept giving them fresh water and dumping watering cans near their favourite cooling spots but really they just looked miserable. I doubt they slept much in their hot coop. I watered the roof but I don’t think that made much difference. Mainly I’m thankful this heat wave didn’t hit when Bronwyn was so sick – I suspect it would have quite literally been the end of her.

As for me, I stayed inside as much as possible. I don’t have air conditioning but I do have a fan. It may not work quite as well as the bees air conditioning but I survived.

I awoke to a pleasant 22 degrees and happy chickens and bees. Let’s hope it stays well below 40 for the rest of the summer (actually, for the rest of my life, thank you very much)!