The superstition that a red sunrise indicates bad weather is based on the old saying, "Red sky in the morning, sailors take warning". The saying is based on the idea that a red sky at sunrise means there is a lot of water vapor in the atmosphere, which usually indicates that rain is on the way. The concept is over two thousand years old and is cited in the New Testament as established wisdom that prevailed among the Jews of the 1st century AD by Jesus in Matthew 16:2-3.