Mat 16:2 When it is evening, you say, fair weather: for the sky is red.

This verse and the next are common knowledge among people who live close to nature. "Red sky in the morning, sailor take warning. Red sky at night, sailor's delight." There is an interesting connection here between fire and heaven. Fire is usually associated in Christianity with punishment, but reading the Greek, Christ is more often referring to the productive use of fire, the baking of bread. Here, however, he is focusing specifically on using the appearance of things and their timing to predict the future.

"Fair weather" is from eudia, which means "fair weather" and is a metaphor for tranquility and peace.

"Sky" is from ouranos, the word translated as "heaven," the dwelling place of God. It means the "vault of heaven" specifically, that arc of the sky. The same word is used to describe the ceiling of a vaulted room, the roof of the mouth, and a tent or pavilion. It is also used to mean a "lid."

"Red" is from purrazô, which means "flame colored sky." It is from purros, which means "flame-colored."