When looking at the sky during the night or morning, the redness of the sky could predict the weather. Sailors say, "Red sky at night, delight red sky at morning, sailors take warning As sailors crossed the threshold into night, right before the sun sets, and saw that the sky was red, it generally indicated that tomorrow's sailing would be clear of weather. When the sky is clear, the setting sun lights up the sky with a red-orange hue, which means the air to the west is clear as many non-cyclone weather systems in the Northern Hemisphere move from west to east. But when the sky is red in the morning, it means the light from the sun in the east is hitting cirrus clouds in the atmosphere and bouncing off the ice crystals within the clouds. Since cirrus-type clouds usually precede a storm, sailors would be ready to batten down the hatches if the sky was red in the morning.
