If it's raining, then obviously it's not very cold outside. Unless you're in the habit of cranking your furnace up to tropical temperatures I guess. For me, I keep the temperature above freezing inside but otherwise? I put on a sweater and open the window. It's cheaper, refreshing, and better for the environment. Right now it's 8 C outside; with the window open and a sweater on, I'm as comfy as a clam.

Ok but you must that this is unusual and most people keep their thermostat around 21 C.