We have an indoor thermometer at our house.
This is what it looks like:
We don’t even have to open the curtains to read the level of frost on the grass or turn on the TV to hear the weather report.
If the cat goes to the heater vent we know we need the warmest coats, scarves, mittens and maybe even boots or an extra pair of socks.
This is cat happiness as well as a useful member of the family.