Reading the Wired story on cats and boxes last week I was introduced to the cat's "thermoneutral zone." This is the temperature range at which animals do not expend any additional energy trying to stay warm (or cool off). For cats, this range is believed to be between 86 to 101 degrees Fahrenheit (for comparison, for dogs, the "TNZ" is more like 68 to 95, with much more variability and tolerance for lower temps)! Because most of us wear clothes, the human TNZ ranges between 64 and 72.
I realized how sad so many kitties must be that we domesticated them and took them away from their desert lifestyle. Are our poor cats constantly shivering and miserable? Well, feline happiness may depend on two things: where the kitty lives, and how much the cat's human warms up the environment.
Living in the Bay Area, we have a few issues: poorly insulated housing, bad heating, and a rather low and unchanging range of temperatures. In 2014, monthly average temperatures where I live were (in order, January to December): 52, 54, 59, 59, 63, 63, 67, 67, 67, 64, 57, and 55, with max temps of: 77, 73, 78, 89, 91, 86, 90, 78, 83, 92, 73, and 68. We had a mere EIGHT days in the cats' TNZ - meaning days where the average temperature was 86 or above (thank you Weather Underground!).
At times, my own cat has taken to sleeping on our floor heating grate for warmth from the gas pilot (conjuring images of Harlow's monkeys).