First time I have seen the water freeze on the glass in the house.
I have seen it in an unheated conservatory before but not the house.
We do the doors dry.
If there's a window over the door, brush any standing water away and put some salt down - proper clean salt not that dirty stuff with sand in it.
Txt customers to warn them of possibility of ice and the salt, it's probably dark when they arrive home.
Bit if a faff but at least we're still working.