So I have seen this happening for the last couple weeks that even with cold weather of -10 to -15 Celsius (5 to 15 Fahrenheit for the American friends or some old-timers here) that I have bees dead in the fresh snow in-front of the hive. (this is my first winter by the way). Today for example it is sunny and calm but -10C (15F) and it snowed last night but there is about 30 bees dead in the snow already today and as I stood there for about 5 minutes I watched a healthy looking bee fly out and circle around for 20 to 30 seconds and then plummet into the snow and freeze up. This happened with the next 2 bees that followed as well all in this 5 minute span. I can only assume this will continue throughout the day, I am not sure why they would come out when it is so cold and this started right from when it first got cold so they should not be in desperate need of a cleansing flight yet and they have lots of food, treated for mites in the fall and a new and health queen in late summer.
Some idea's would be helpful,