They are frequently used interchangeably. "Blue sky" is more poetic or lyrical in nature. "Blue skies" is more accurate or scientific.
Skies [plural]: the sky in a certain state or location: We enjoyed clear blue sky for weeks. We're on our way to sunny Florida. As far as I can determine, using the plural form when referring to the weather or the sky in a certain state or location is OK.
I saw some clouds in the distance, so I knew it would rain soon. The sun came out just in time to catch a glimpse of it going down. I heard that it rained cats and dogs (or something like that) - what a great day for a walk!
People often ask if they can say "blue skies" in English. You can indeed say "blue skies" in English. It means there are no clouds in the sky and so it is possible to see all the way to the horizon. Many people think that you cannot say "blue skies" because it is not natural language but this is not true. You can also say "green trees" or "white snow" if you want to refer to different colors or elements in the environment.
You should know that in American English, people usually say "clear skies" instead of "blue skies".
The term "sky blue" refers to a specific shade of blue that is on the lighter end of the blue spectrum. @Duong Bao Nhi "Blue" is a broad term that might refer to anything from a very light blue to a deep navy. The phrase "blue sky" is used.
The sky represents spirit, tranquility, and paradise. A clear blue sky denotes joy and tranquility. Dark clouds in the sky, on the other hand, represent tumultuous times in your life. They may also signal a coming storm or tragedy.
A deep blue sky with no clouds indicates a time of great peace and prosperity. White clouds, with just a few dark ones scattered here and there, mean that difficulties will come but they will not last forever. Many white clouds seen in one day are said to bring good news of some kind.
A bright blue sky with many white clouds is usually an indication that something joyful is going to happen soon. For example, if you see this picture of a blue sky with many white clouds, it would mean that you should have hope and be patient because your goal seems very far away but you will reach it eventually.
A red sky at night means that there is going to be rain, and if the sky is black with no moon, then there's a chance of thunderstorms.
A green sky at night means that there's going to be sunshine, and if the sky is yellow or orange, then there's a chance of heat waves.
I suppose we have the plural "skies" because our mental understanding of a, or the, sky varies from the scientific or meteorological definition in that it considers the multiplicity of variations (location, time, weather) to be various skies. That said, I'm not sure how common this use of the plural is.
If the sky is a blue dream, it represents a confident and joyful dream that has gone just as intended. A blue sky might also be taken as a foreshadowing of the next journey. If you see stars in your sleep, it typically means you've made a lot of money. When you see an overcast sky, it represents sadness. Clouds in dreams often indicate anxiety or worry. A dark blue sky with lightening behind it or a bright yellow one is a warning sign that something terrible will happen soon.
A clear blue sky is always a welcome sight. It means that whatever you dreamed about last night came true. A white cloud-free sky is evidence that you have good fortune coming your way. If the sky is red or orange, there is danger ahead. A purple-black night sky is a bad omen; something tragic is going to happen.
Seeing plants in your dream, means prosperity and happiness. Flowers mean love and joy. Trees are signs of power and success. Grass is common and easy to find; it represents wealth and security. Mowing the lawn is a sign that you will have success at business or career. Weeding is related to finding freedom from addiction. The color green in your dream means health, hope, and peace. White flowers are for lovers, mothers, and saints. Black flowers are for funerals and evil spirits.
Aliens in your dream mean new opportunities and adventures. Being abducted by aliens is similar to being kidnapped.
Cloudless and vivid, wonderful windy, obviously cloudless, totally cloudless, only darkish, pink and shy, graciously clear, chilly but bright, almost cloudless, wide and sunny, almost cloudless, amazingly bright, plain and bright, cloudless, nearly eternal, somewhat hazy.
The color of the sky is called "celestial" or "auroral" blue because it resembles the color of the aurora borealis. It is made up of various wavelengths of light from the spectrum that are reflected by particles in the atmosphere, especially clouds. The color of the sky can vary depending on the type of cloud cover present as well as the time of day. During the day, when the sun's rays are bouncing off many different kinds of particles, its color varies from pale to deep violet. At night, when there are no clouds present, the sky is black with a thin layer of stars visible through the naked eye.
In art, music, and literature, blue often indicates truth, honesty, loyalty, infinity, air, water, heaven, emotion, sadness, melancholy, wistfulness, joy, hope, imagination, awareness, perception, intellect, logic, despair, doom, drunkenness, illness, weakness, violence, terrorism, freedom, romance, sexuality, fertility, protection, peace, paradise.
IDIOM: Clear sky. An unduly optimistic attitude or temperament. Precise (2). It everything seemed so bright when they left out—-away to the West, to the Denver conference, nothing but sunny sky ahead. A very common expression used in American English to indicate that whatever problem one is facing, it has a solution. Also, as a slogan.
Example: "Blue Skies Ahead!" is what the baseball team at your school says when it wins a game. This idiom has become so popular that it has even been used as a song title by an American band.
Origin: This expression dates back to at least 1918 when it was written into a cartoon drawn by John T. McCutcheon for the Chicago Tribune. The drawing depicted a young boy saying goodbye to his family after they moved away to take jobs in California. Under the heading "Clear Sky Ahead," the boy's father wrote him a letter saying that things would be all right because "the clouds have rolled away."
Even though this expression is popular today, it did not immediately catch on. In fact, the first documented use of "Blue Skies Ahead!" was in a 1992 episode of Disney's Batman television series. However, it wasn't until five years later that it became more popular after then-President Bill Clinton used it during a campaign speech to describe his hopeful vision for the country.