We've got mid-50's today and mid 40's tomorrow. Temps will get down to 25 tomorrow night.
The difficulty is convincing the bees to TAKE syrup when its that cold at night. If you warm the syrup, and the temps get warm enough for them to begin moving, they may take it. Then you may lose them form the excess moisture.
THis is why it is important to get the syrup into the hives in the fall so they store it, and then use it during the course of the winter.. I did pump the syrup to them in the fall, but they used it as fast as I gave it to them. The result is, that I am feeding sugar because that is all that they will take, and what can be safely given. I have lost two hives to Nosema so far. I can promise you I wont make this same mistake again.