1) I can tell the temperature in the morning by the action of the storm door. If it is below -15, there is no pressure in the pressure door closer thingy. So the door slams, and it's cold.
2) I can tell the temperature by the bedroom floor. If it is below -20, my feet will go numb in less than a minute. It's cold.
3) I can generally, but less accurately, tell the temperature by how my nose feels when it's sticking out of the nest of down comforter and wool blanket. It depends largely on whether I stoked the wood stove in the middle of the night (most nights unfortunately I cannot muster whatever it takes to do that!)
4) My car will start at any temperature it has encountered thus far. The battery gets a bit sluggish when the temperature is below -30.
5) The creak of the compacted snow underfoot sounds a lot different at -30 than it does at 0.
6) When you set out with the specific goal of seeing a snowy owl, you will not find one.
And so it goes.