green sky

Why, when theres going to be a bad storm, does the sky take on a weird greenish tint?

I have no idea why, but I’ve seen it happen when weather is at it’s worst.

IMHO–dust in the air?

A “USA Today” article which seems surprisingly factual, and provides some links to scientific papers at the bottom. Unfortunately, only the last of the three seems to work:

The third and fourth paragraphs sum up two major theories:

The abstract of the scientific paper linked to at the bottom mentions both of these as well, and says they may not be mutually exclusive - both effects may be at work.