I have been beekeeping for around 5 years and have not seen the winter temperatures stay so low for so long. Going into the winter the hive population has to be strong, because it is a cluster of bees constantly buzzing their wings that keeps the inside of the hive 92 degrees, no matter how cold it is outside. The bees cluster around the queen, keeping her warm, and migrate around the hive to eat the honey stores and fuel their wintertime efforts.
Going into the winter this year, I had one strong hive, and one not-so-strong hive. Unfortunately, the weaker hive was lost in December 2017. Although there are various reasons a hive can die, I am thinking that there was simply not enough bees to maintain a warm hive. December had a string of multiple days well below freezing, and January 2018 has been even worse.
When we get a warm day, above 50 degrees or so, you often can see a few bees exiting the hive, and I saw just that on the latest warm day in January with my strong hive. But a quick peek inside the weaker hive showed a bunch of dead bees laying around. I will keep the honey from this dead hive and use it to feed the living hive if needed.