Early in the morning, when the sun is just coming out, or in the evening when the sun is setting, the clouds in the sky are often reddish, like fire. People call this reddish cloud, the burning cloud, also called the morning and evening sun. Sometimes, when there are no clouds, the sky is also a fiery red color, which is called a fiery sky.

So how do fiery clouds form?

We already know that the sun is made of a mixture of seven colors of light: red, orange, yellow, green, cyan, blue and purple. Of these colors of light, red light has the greatest ability to pass through layers of air, orange, yellow and green light is second, and cyan, blue and violet light is the worst. When there are no clouds in the sky, there are fewer raindrops hanging in the air; the air layer is thinner at noon, and almost all of the red, orange, yellow, and green colors of the sun's light passes through, stopping only the blue, blue, and violet colors of light, which are reflected by the blue light the most, and so coloring the whole sky blue.

When the sun rises in the east in the early morning or sets in the evening, the sunlight reaches the ground and passes through a thicker layer of air than when the sun is overhead at noon. Sunlight in the yellow, green, green, blue, purple several kinds of light, in the air layer in the walk not much far has been exhausted, can not pass through the air layer. Only red and orange light could poke its head through the air layer, coloring the sky red.

Fire clouds can predict the weather, the folk proverb "early burn do not go out, evening burn travel thousands of miles", that is, fire clouds or fire sky if the morning, the weather may be bad; appeared in the evening, the next day will be a good weather.