Answer:
It creates a sarcastic tone.
Explanation:
The definition of the word <em>balmy </em>is <em>characterized by pleasantly warm weather.</em> This word is used to describe the minus 20 degrees, which is horribly cold, but still not as cold as Alaska usually is. This combination of words creates a paradox - how can minus 20 degrees be balmy? It is not - the author is just being sarcastic. That's how the use of the word <em>balmy</em> creates a sarcastic tone.
The first analogy is abstract. The second analogy is concrete. Shakespeare: plays:: Mark Twain: Novels; screen: computer:: face: watch. Sorry, I'm not sure how to prove the concrete/abstract part but I'm sure that I'm right.