Here's what the comparison implies:
* Dim Sun: The sun is described as "dim," suggesting a cloudy or overcast day.
* Nickel Sky: A nickel is a small, flat, silver-colored coin. Comparing the sky to a nickel highlights the following:
* Color: The sky is a dull, grayish color, similar to the color of a nickel.
* Size: The sky appears small and constrained, as if it's been compressed into a tiny space, just like a nickel.
* Shape: The sky seems flat and featureless, lacking the usual expanse and depth of a clear sky.
Therefore, the simile paints a picture of a gloomy, overcast day where the sun appears small and insignificant, like a mere coin hanging in the sky.