How Bees Manage Temperature and Moisture

My beekeeping journey began when I was a teenager in the early 1970s. School and work soon took me to the big city and away from my honey bees. Four decades later, I had the opportunity to move back to the country and renew my passion for honey bees.

I knew that living in a different part of the country and four decades of change would present new challenges. I was ready for those challenges…or so I thought.

My first winter, I lost four out of five hives. When I opened each hive in the spring, I found a ball of dead moldy bees. Moisture had condensed and rained down on them. What had I done wrong?

My intent in this article is not to offer a single solution that will apply to all beekeepers looking to manage moisture. What works for me on the North Olympic Peninsula may not work elsewhere. My intent is simply to share what I and others have done to control moisture for our own experiences.

Choose a Favorable Location

It has been said that the most important aspect of determining the value of real estate is “location, location, location.” That is also true for honey bees. When honey bees prepare for a new home, they send scout bees looking for the best location. A beekeeper deciding on a place to position a hive, like a scout bee, must search for a prime location.

A favorable location depends on the local climate. When keeping bees in Mississippi, I looked for an area that provided shade. Here on the North Olympic Peninsula, I look for a location that provides sun and allows air to circulate.

Kate, one of our PerfectBee Ambassadors, lives in the Willamette Valley in Oregon. She describes the climate in her area as “wet, wet, wet.” Kate describes her hive location:

I have located my hives on my back deck against my house, with a rain cover over the top. I usually put pine shavings, old t-shirts or some other kind of moisture-absorbing substance in my Vivaldi top on each hive. Even with all of that, I still get mold growing some winters. . . very frustrating.

In searching for solutions for moisture issues, I discovered that most of my property is in a frost pocket. A frost pocket is a low area of land with poor aerial drainage. Cool, moist air settles into these areas and is trapped. The temperature in a frost pocket may be several degrees colder than the surrounding areas.

Frost pockets occur downwind from solid barriers. Such barriers occur in the shadow of a hill or a manmade structure. Even a solid windbreak can create a frost pocket.

I partially resolve my frost pocket issue by placing my bee hives on a south-facing slope on the north side of my property. To provide air circulation, my hives are about two feet off the ground. A line of trees protects my hives from winds blowing from the north.

Assure that Bees are Ready for Threats

Once a prime location has been chosen, a beekeeper’s most important role is to ensure that bees are ready to deal with threats. Most beekeepers are aware of the need for honey bees that are equipped to deal with threats like Varroa Mites. It is just as important for bees to be able to deal with threats like moisture.

Purchasing bees from local stock helps to ensure that I have bees adapted to my climate. If I cannot find a local nuc or package, I requeen as early as possible using local queens from a reputable source.

Even more important than having a local source for honey bees, is to assure that bees enter winter with a large, healthy cluster. The larger the cluster, the more efficient bees are in moisture control. If I have a questionable size cluster, I will combine two hives.

Do Not Add to the Work That Bees Must Do

Bees, just like humans, put moisture in the air when they breathe. The more active the bees, the more moisture they put in the air.

As I am writing this article, my grandson is in and out to play in the snow. Each time he opens the door, I feel the temperature in my house drop. The heat system kicks on and the electric meter starts spinning. The same thing happens in a beehive. Any time the cluster is broken, the temperature drops. Bees must fire up the heater bees to rewarm the cluster. In the process, moisture is produced.

After mid-fall, I disturb my bees as little as possible. They have begun making their own preparations for winter. Comb is shaped and propolis is added. Cracks between boxes are sealed. The hive is ventilated according to their liking. If I disturb their work, they not only have to redo their work but in doing repairs, they release more moisture.

It is hard to resist the temptation to open a hive to see how the bees are doing, but our curiosity can kill our bees. Rather than open a hive to see how my bees are doing, I use a stethoscope to listen for activity. Some beekeepers use thermal cameras. I occasionally tap lightly on the side of a hive and listen for increased activity within, but even this small act interferes with a tight cluster.

Beekeepers can cause more work for honey bees by feeding sugar syrup in late fall. Sugar syrup, like nectar, must be condensed to between 14% and 21% moisture. Any moisture beyond that percentage must be released into the hive as bees condense their food.

My goal is to make sure that my bees have adequate honey stored by the time the fall nectar flow ends. I keep a few frames of capped honey in my freezer. If a hive does not have adequate stores by mid-fall, I either switch frames from a hive that has more stores than they need or pull frames from the freezer.

It is possible that feeding bees late into the fall disrupts their sense of nature, signaling them to raise winter bees. These “fat bees” or winter bees store nutrients in their bodies and are better equipped to deal with all winter conditions. Having extra energy stored in their fat bodies means there is less moisture released from the processing of food.

Prevent Condensation from Raining on the Bees

The main threat from moisture occurs when warm moist air rises and condenses on the first cold surface it touches. This is usually the roof of the hive. I go overboard in insulating the top of my hive.

Condensation at the top of the hive falls back into the hive, drenching and chilling the bees. If this moisture does not land on the bees, it may still kill them. Moisture on comb creates an environment for mold or freezing. Mold creates an environment for disease. Frozen comb may prevent bees from accessing stores.

If moisture freezes on comb, a beekeeper may never be aware that comb has frozen. By the time a hive is opened in the spring, ice has melted. There may be plenty of honey left in the hive, but the bees have starved.

Beekeepers take two approaches to dealing with condensation. The first approach is to prevent condensation from occurring. The second is to capture and remove condensation if it occurs.

In some climates, condensation can be prevented with ventilation. In home construction, a formula of 500 to 1 is used in attic ventilation. For every 500 square feet of attic space, there is one square foot of ventilation. Using this formula for a bee hive, a lower entrance the size of the smallest entrance on an entrance reducer and a similar-sized upper vent is adequate. More ventilation than this creates too much air movement and chills the cluster.

Some beekeepers add an upper entrance for ventilation. Others take simple steps like adding a popsicle stick under the inner cover. I use a moisture box with vents near the top of the box. The vents in my moisture box are much larger than called for by the 500 to 1 formula, but the free flow of air through my hives is blocked by the absorbent layers in the moisture box.

Judi, another PerfectBee Ambassador, lives between the Catskills and the Adirondacks. Here is how she manages condensation:

Once the weather is too cold for my bees to be flying, I place spacers with upper entrance holes on each hive. These are used to hold candy boards, as added insurance. The supers go on that and have screened bottoms with wood chips inside. On top of this, I place foam insulation or moisture boards. Last is a telescoping cover. I also wrap the hives with roofing tar paper . . .

Lower entrances must be checked periodically to make sure they are not blocked. I check my hives at least once a week during the winter.

After a recent snowstorm, I found the lower entrances were blocked with snow. The fresh snow did not stop ventilation but did prevent the bees from doing house cleaning. Dead bees collected at the entrances, blocking the flow of air. Anytime I check my bees in the winter, I carry a stiff piece of wire with a hook on the end. I can quickly and gently run this wire into the opening to pull out dead bees.

In extremely wet climates, ventilation will not be enough to prevent moisture problems. Ron, a PerfectBee Senior Contributor, describes some of the additional steps he takes:

What I observed in my hives was that the strong (larger colonies) hives kept the mold out of the frames and under control. The smaller colonies, while normally surviving the winter, never got out to the outer frames and that’s where I would find mold growing.

It was this observation that led me to replacing the outer frames with moisture boards. I also used a quilt box with wood chips, on top of which I lay burlap. The burlap tends to draw the moisture up and out of the wood chips. I can then easily remove the telescoping cover, remove the damp/wet burlap and replace it with a dry one. Certainly not a cure all but it definitely helped.

Many beekeepers successfully use the Mountain Camp method of putting dry sugar on newspaper above the top frames to absorb moisture. If this method works for you, use it. The only year I used this method for moisture control, it worked in about half of my hives. In the remaining hives, the sugar turned to sugar syrup and drenched my bees.

Any method used to absorb moisture needs to be checked occasionally to make sure that it is not saturated. If saturated, it needs to be replaced. A well-designed moisture box of a Vivaldi board allows for saturated material to be lifted out and replaced with minimal disturbance to the bees.

Here is a rough sketch of the top of my hives and a picture of one of my hives:

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With my hive set up in this manner, the roof of my hive is not the first cold surface that rising moist air contacts. My methods are extreme, but so is the climate where I live.



There are many other steps that can be taken to control moisture. Do not be afraid to try different methods. Keep a record of what works and what does not work. Do not believe that anyone has a perfect solution for every climate. Learn from your bees.