VTBeeHannah · Vermont, US · Beginners · Oct 26, 2026
When does the winter cluster actually form, and does it break up again on a warm afternoon?
Vermont, second year. I've read the word "cluster" a hundred times on this forum and I realise I don't understand the mechanics of it, which makes it hard to judge anything I'm seeing.
This week has swung between -2°C at night and 15°C on Saturday afternoon. On Saturday there were bees flying and the hives looked like they do in September. On Sunday morning at -1°C I put my ear to the side and heard a low steady hum and nothing at the entrance at all.
So what's actually happening? Does the cluster form and break up with the weather, or does it form once in the autumn and stay until spring? At what temperature do they commit to it? And when they're clustered, what's the temperature inside — I've seen numbers from 20°C to 35°C quoted and I assume the difference is whether there's brood.
The reason I care isn't curiosity. I want to know whether Saturday's flying was a good sign or a waste of their reserves, and whether the fact that they're using stores faster on a mild week than a cold one is real or something I've invented.
It's dynamic, not a switch. Bees start to gather loosely below about 14°C and tighten as it gets colder; above roughly 10-12°C in sun they break and fly. So your Saturday and your Sunday are both normal for the same colony. Inside a broodless winter cluster the core sits around 20-25°C, which is much cooler than people expect. Once they rear brood again in late winter it goes up to about 35°C, and that is when consumption really climbs.
AlpineCarnica · Oct 26, 2026
And your last question: yes, it's real. A mild fluctuating winter costs a colony more stores than a steady cold one, because they keep breaking cluster, flying, and burning fuel. Beekeepers in mild maritime climates feed more emergency fondant than we do at -15°C, which surprises everyone the first time they hear it.
QuebecBees · Oct 26, 2026
Quebec. Saturday's flying was good, not wasteful — that's a cleansing flight, and after a few weeks confined they need one. Bees won't void inside the hive if they can help it, so a mild afternoon in late autumn is a gift. VTBeeHannah, look at the snow or the hive fronts afterwards: yellow-brown spotting after a flight day is normal and healthy.
VTBeeHannah · Oct 27, 2026
That explains the spotting on the roof I was quietly worrying about. And the mild-winter-costs-more point is not what I expected at all — I'll keep a closer eye on weights in a warm January.