It looks like the weather is going to turn to some more normal temperatures.
The forecast has highs in the 30's later in the upcoming week. So covering the hives anytime would be ok for the bees. Even if it hits the low 60's for a day, the bees will be ok.
If you haven't treated for Varroa yet. A treatment with oxalic acid will help keep your mite levels low through the winter.