The reason you know it is cold or warm is because your sense of touch gives you that information.
You see colors and shapes.
You hear sounds and music.
You taste foods.
You smell odours.
Now, what is your sense that measures tiny changes in magnetic or electrical vibration around you?
The closest you get to it again, are your feelings.
Right now, you are not yet equipped with a trained sense or tool that allows you to perceive biofields.
Now, imagine that 100 years from now, you could be walking around with a tiny cell-phone-like camera that let's you see other person's biofields.
You could measure it physically, see disturbances in the biofiled activity related with unsolved emotions.
You could actually see a person's happiness streaming through their whole body in a complex sea of energy lines.
Imagine!
http://vitalcoaching.com/biofield.htm