As already mentioned, shuck those plastic wraps, they keep in humidity and they sweat on the inside.
Do you have the top entrance?
Bees in that kind of cold (a bit nicer than ours) they need top entrance. If not for nothing else - the cluster is on top and for them to get out, they have to go all the way down and out. In winter, on a warm day, it is still too much for them and they don't make it back up.
If one has the top entrance... By "entrance" I mean, a cut notch in the bottom side of inner cover rim, (1/4" x 2.5 - 3" !) There they have only a short hop to the outside and when they realize that is cold, they can get back, pronto!
Some, here and there, will stay out, but nothing like you have on those pictures. . .
They also need quiet. They are especialy sensitive on vibrations.
Who knows, who or what, disturbed them when you were away? Something made them come out when they should not!?
I went visit mine last Saturday and had to leave right away, cause they knew that I was there, by only walking around on snow.
(but I also forgot to turn off the Critter Gitter)
They were coming out and falling in the snow. It was only one degree C. But they are all still there and God willing, they will be there when the spring arrives?
It looks like it may be early this year?
Good luck, fellow countryman...