An Internal Thermometer for External Temperatures?

It's remarkable how much easier it is for me to get up and get going in the mornings when it's nice outside. It doesn't make sense because most of the time, even if I have my window open, I can't really tell what the temperature is like outside when I wake up. Somehow my body just knows which days it is going to have to deal with miserable weather and which days it will actually be halfway comfortable.