'Sky' in the Bible

"A farmer went out to sow his seed. As he was sowing, some seeds fell along the path, were trampled on, and birds from the sky ate them up.

You hypocrites! You know how to interpret the appearance of the earth and the sky, yet you don't know how to interpret the present time?"

It is like a mustard seed that someone took and planted in his garden. It grew and became a tree, and the birds of the sky nested in its branches."

Because just as lightning flashes and shines from one end of the sky to the other, so will the Son of Man be in his time.