When one can tell the outside temperature by the hardness and/or level of protrusion of one's own nipples. in other words, your mammaries are a thermometer.
Pedestrian 1: "Wow it's colder outside than I expected."
Pedestrian 2: "Yeah, my thermammeters are reading 10 degrees"
Pedestrian 1: "I believe you, they're poking through your shirt"
When you can look at your house cat and can tell what the temperature is by their body position.
1. Curled up in a ball = 60 degrees
2. kitty loaf style = 65-70 degrees
3. On side with legs out = 70-80 degrees
4. Layed out on side with body and legs stretched way out = 80-90 degrees
An empty Coors Light "cold activated can" left out side of a window to determine if it is warm, cold or "super cold" outside. Works best in colder climates.