I have a colonial house. Last night we had hot water in our master bathroom upstairs. Overnight temps were in the single digits... When we turned the knob in the upstairs sink or shower for hot water we get drips. The cold water knob works and cold water comes out. What could the problem be? Water tank is less than 6 months old it is a Weil Mclain and first floor bathroom and kitchen have hot water.

Sounds like frozen hot water line.