A winter cluster keeps itself warm, but it also produces a lot of water vapour. That moisture condenses on the cool hive walls and roof. The UK National Bee Unit puts it plainly: it is the damp, rather than the cold, that kills bees. So this month, look at how water gets out of your hives, not just how heat stays in. Three simple checks: make sure the roof doesn't leak, keep hives up off the ground on proper stands, and tilt each hive very slightly forwards so condensation runs out of the entrance rather than pooling on the floor. If you use open mesh floors, the NBU says you can take the floor inserts out over winter, unless your apiary is very exposed to wind. Usually the roof, entrance and floor give enough ventilation. If you insulate in a harsh-winter area, keep that ventilation in place. This is winter advice for the Northern Hemisphere; in the Southern Hemisphere, November is spring. Mesh floor open or closed over winter: what do you do, and has it made a difference?