Winterising Your Hives in the Nordic Climate
Swedish winters are long and dark. This guide walks through the specific challenges of overwintering bees in Scandinavia — insulation, ventilation and food stores.
Swedish winters are among the most challenging in Europe for honeybees. In central Sweden, colonies may be confined to the cluster for five to six months — from October through to late March. In the far north, that period extends even longer. Preparing correctly in August and September determines whether your colonies emerge strong in spring or don't emerge at all.
The Biology of the Winter Cluster
When temperatures drop below about 8°C, honeybees stop flying and form a cluster. The bees pack tightly together, vibrating their flight muscles to generate heat. The cluster maintains a core temperature of around 20–35°C throughout winter, consuming honey stores as fuel. The queen is at the centre of the cluster. She stops laying in October, remains dormant through the darkest months, and resumes laying in January or February — often before the beekeeper even opens the hive for the first spring check.
Critically: bees don't die from cold — they die from starvation and condensation. A colony with adequate stores in a dry hive will survive -30°C. A colony with poor stores or a wet hive will die at -5°C.
Step 1: Final Autumn Inspection (September)
Before October, complete a thorough inspection:
Check for a young queen. A colony heading into winter with a queen from the current year (raised in summer 2026, for example) will perform far better than one with a two-year-old queen. If the queen is old and the colony was not strong in summer, consider combining it with a weaker colony rather than trying to overwinter both.
Check for disease. Look for signs of European Foulbrood, Nosema, or heavily varroa-damaged bees (crawling bees with deformed wings). Treat varroa before it is too late — see our varroa guide for timing.
Assess colony size. A strong colony going into winter should cover at least 6–8 frames of bees. Weaker colonies struggle to maintain cluster warmth. Combine small colonies.
Step 2: Food Stores
This is the single most critical factor. In Sweden, a colony needs a minimum of 15–20 kg of stores to survive from October to late March. In northern Sweden or harsh years, 20–25 kg is safer.
Autumn syrup (August–early September): Feed 2:1 thick sugar syrup (2 kg sugar : 1 litre water) as early as possible — before the end of August if you can. Bees need time to process and cap the syrup before the cold sets in. Feeding in October is largely pointless as bees cannot evaporate the moisture from thin syrup once temperatures drop.
Candy/fondant (emergency top-up): Fondant or bee candy can be placed directly on the top bars throughout winter and does not require processing. Use it if stores look low in November or as a precaution in all hives. A 1–2 kg block placed on the top bars takes up no extra space and can save a colony in March when stores run out but weather is still too cold for the colony to break cluster.
Check stores in late February. Lift the hive from the back. If it feels light, add candy immediately.
Step 3: Insulation
Bees generate their own heat — your job is to reduce heat loss, not to add heat. The key areas:
Roof insulation: Place a 5 cm slab of polyurethane foam inside the roof or hive lid. This is the single most impactful insulation improvement. Heat rises; an uninsulated roof loses the cluster's generated heat rapidly.
Side insulation: Less critical than roof insulation in a wooden hive, but hive wrapping with purpose-made hive coats (available from Swedish suppliers) or roofing felt helps in very exposed locations.
Avoid floor insulation: The mesh floor (varroa floor) should remain open — ventilation from below is important.
Step 4: Ventilation — The Critical Factor
Condensation kills more Swedish colonies than cold. A winter cluster of bees produces significant moisture through respiration and metabolism. If this moisture cannot escape, it condenses on cold surfaces inside the hive and drips onto the cluster — chilling bees and promoting fungal growth.
Top entrance: In addition to (or instead of) the main bottom entrance, provide a small top entrance (a drilled hole of 20–25mm, or a thin gap under the crown board). This allows warm, moist air to escape from the top of the hive. Many Swedish beekeepers swear by top entrances as the most important winter measure.
Mesh floor: A mesh (varroa) floor provides ventilation from below and reduces humidity. In most of Sweden, a mesh floor does not make the colony significantly colder — the cluster regulates its own temperature.
Absorbent material: Some beekeepers place a piece of hessian or absorptive material on the crown board to soak up excess moisture.
Step 5: Mouse Guards and Wind Protection
Mouse guards: Essential. Mice will enter a hive in autumn and cause serious damage — destroying comb and disturbing the cluster. Fit a metal mouse guard (a strip with 7mm holes, which bees can pass through but mice cannot) over the entrance by the end of September.
Wind protection: If your hives are exposed, fit a windbreak. Cold wind accelerates heat loss from the cluster and causes bees to consume stores faster. Even a simple wooden board on the prevailing wind side makes a measurable difference.
Spring: The Critical Transition
March and April are when most winter losses occur — not from cold, but from colonies expanding faster than their stores can support. The queen begins laying in January–February; by March the colony is raising brood but the first nectar is still weeks away. Check stores in late February and add candy if needed. The first warm day above 12°C (usually late March in central Sweden) is the day for your first spring inspection.