The temperature of the ocean water off the Oregon coast...
50°F, 10°C. The temperature in the top floor bedroom when it has been cloudy and cold. The temperature of the main floor after a few sunny days. When it's cloudy and cold, or rainy, the main floor is in the 42°F range. I use the refrigerator thermometer to tell me what the temperature is inside on that floor, since the thermometer on the non-functional thermostat only goes down to 52°F.
When it has been warm & sunny, the top floor can be up to 60°. Passive solar.
I worked outside for over 7 years. I know how to live with this. Lots of layers, lots of blankets. I have a fleece-lined denim men's bathrobe that I call a housecoat, replacing an old wool one of my Dad's. I wear it over lined jeans and several t-shirts and a fleece vest. I sleep in layers, including a hooded sweatshirt, with mounds of blankets. When it's really cold, I add a sleeping bag to the stack on the bed. Plus heater cats, who sleep on me.
I have been trying to keep the electric bill in the $75 range this year, instead of the $300 range of previous years, a legacy from when Enron and the Bush/Halliburton regime screwed California. And still keep the house warm enough to not get moldy.
When the chimney is clean and I can use the wood-stove, it can get positively tropical - over 60°. T-shirt temp.
One of the advantages of these interior temperatures is that there are more days, like today, when it got up to 59° outside on the sunny South porches, when it is possible to have the windows and doors open to air out the house and warm it up.
One of the disadvantages is that in the morning, crawling out of that warm nest is unattractive, and the temptation to go back in with a book and cup of tea, when I wake up early, is irresistible. And then, falling back to sleep... And then running down the hill, almost late to work.
(One other trick - I warm up my clothes & pajamas on the radiator heater, for a few minutes before putting them on. Natural fibers only, not synthetics which might melt. And not with the heater turned on high. And don't leave the room and forget them.)