When the temps dip below zero, the store bought spigot covers will not do the job. The spigot will still freeze up unfortunately, we do not have a frost free spigot.
To the workshop I went and came up with the cover you see above. There is a thermal cube in the bottom of the housing that turns on a 40 watt light bulb at 35 degrees and off at 45 degrees.
This coupled with some blankets covering it will keep water flowing down to 17 degrees below zero (air temp), which is the coldest we have had since moving here.