Inside a hive in winter, bees do not try to heat the whole wooden box. They keep a tight group, the winter cluster, warm, and let the rest of the hive stay cold. The exact temperatures vary with colony size, weather, and whether there is brood, so the figures below are approximate.
The short answer
In winter the core of a cluster is typically kept far warmer than the surrounding air, while the cluster’s outer layer is much cooler. The colony adjusts its heat production to the weather, using more honey in colder conditions.
How the winter cluster works
When outside temperatures fall, bees gather around the queen (the job of the queen). The cluster has two broad layers:
- An outer shell of bees packed together that acts as insulation. These bees are cooler and mostly still.
- An inner core where bees generate heat by shivering their flight muscles without moving their wings.
Bees continually move between the shell and the core, so no individual stays in the cold too long. The cluster also expands and contracts with air temperature, tightening as it gets colder.
Temperatures inside the cluster (approximate)
Commonly quoted figures, which depend on source and conditions:
- Bees begin to cluster when air temperatures drop to somewhere around 10 to 14 °C (50 to 57 °F).
- The outer shell is often held at a temperature around 9 °C (48 °F) or a little higher, since bees on the surface must stay warm enough to keep moving.
- The core is cooler when there is no brood, and warmer, roughly 33 to 36 °C (about 91 to 97 °F), once the colony is rearing brood.
Treat these as typical, not exact. Measurements differ with colony size and where the sensor sits.
Brood changes the picture
Brood needs a warm, stable environment, so a colony rearing brood in late winter spends much more energy than a broodless cluster. Many colonies start brood rearing again in winter as days lengthen, which raises honey consumption and means stores matter more than ever in late winter. This is also when many colonies starve. See does a bee hive die in winter for why.
How much honey do colonies need?
Honey is the colony’s fuel. How much is enough depends on climate and colony size. For cold regions, commonly cited advice is to leave a large reserve of capped honey, often tens of pounds, but local guidance is more reliable than a general figure. Our winter preparation checklist discusses how to check stores.
What affects hive temperature
- Colony size: bigger clusters retain heat better.
- Extra space: empty boxes give the cluster more to cope with.
- Wind and exposure: cold wind increases heat loss.
- Moisture: damp conditions make cold harder to bear, condensation can drip on the cluster, and mold in the hive can follow.
- Insulation (see insulated hive plans) can reduce heat loss in cold climates, but should not block ventilation.
What beekeepers should and should not do
- Avoid opening the hive in cold weather, since this disrupts the cluster and loses heat.
- Reduce unused space and keep stores near the cluster.
- Ensure ventilation to manage moisture.
- Use external signs (hive weight, entrance activity, sound) rather than opening.
Can bees survive a cold winter?
Honey bees survive very cold winters in many regions, provided the colony is large and healthy, has enough food and stays dry. Cold alone is less often the cause of loss than starvation, mites or damp.