[evan_au]

I would say that the weatherman is speaking figuratively (=metaphorically) rather than figuratively (=numerically).

One measure for "twice as cold" would be to measure the heat loss through each square cm of bare skin.
- If the weather is "twice as cold" you would lose twice as much heat through each square cm of skin.
- Since heat is carried away more effectively by moving air than still air, on a windy day you could be "twice as cold" and the temperature could be unchanged at 0C.

This is what the various Wind Chill formulae attempt to estimate.
See: https://en.wikipedia.org/wiki/Wind_chill

[Monox D. I-Fly]

Once I asked a question along something of this line in 3 different math forums and they seemed to agree with you guys:
http://mymathforum.com/elementary-math/340359-ask-about-hot-cold.html
http://www.mathisfunforum.com/viewtopic.php?id=23897
http://mathhelpboards.com/pre-algebra-algebra-2/ask-about-hot-cold-21312.html

[Tomassci]

why are some people being so literal ? the weatherman didn't REALLY say that...its a hypothetical question ! 

We didn't know that.

[evan_au]

In a Geezeresque fashion, let me try another answer using the Delisle Scale..  This scale has the advantage over the other scales in that the larger the number, the colder the temperature.

I heard recently that Anders Celsius developed a temperature scale where the fixed points were the freezing and boiling points of water - only his system had freezing point=100°, and boiling point =0°. So it had the same direction as the Delisle scale...

This scale was turned upside down in 1743 by Jean-Pierre Christin, to produce the Celsius scale we use today (well, Europeans and Scientists use it, anyway).
See: https://en.wikipedia.org/wiki/Celsius

[alancalverd]

What about windchill?

Windchill is an attempt by weathermen to "dumb-down" science so they can make meaningless statements like "twice as cold"   []
 
It's pretty qualitative.

No, it is quantitative. Wind chill is the difference between actual ambient and the still, dry air temperature that would produce the same rate of heat loss from moist skin at 30°C. It is tabulated as a function of wind speed, temperature  and humidity in most survival manuals and physiology textbooks.