Why did 22° in winter feel colder than 20° now?

I have a programmable thermostat (great things!) that for the last 6 months has been set to warm the place up to 21.5° just before I have to get up. In winter when it’s -20, -30 outside, it still seemed quite chilly in the morning, and I would often bump it up a bit more 'round about when I took a shower.

The last few days though, I’ve actually gotten (briefly) out of bed to turn the thermostat down 'cause I felt so warm.

My house is fairly old, and as such isn’t super-well insulated… could radiant heat from the walls be making such a big difference? And if so, why do all my thermometers still agree that the house is cooler now, when it feels so much warmer? :confused:

Radiant heat, or cool, from windows etc. is undoubtedly the reason.