The sky turned dark, and the rain started.

Meaning: It's talking about the weather changing. It went from being light to dark, and then it started raining.

Choice of Words: Sky is the area above our heads. Dark means not much light, like nighttime. Rain is water falling from the sky. Started means it began. So, the sentence describes a change in weather.

Alternative Expressions

The sky got all gloomy, and the raindrops came down.

Meaning: This means the same as the first sentence, but it uses different words to describe what happened.

Choice of Words: Gloomy means dark and sad. Raindrops are the little drops of water that make up rain. Came down means fell from the sky.

The clouds covered the sun, and the heavens opened up.

Meaning: This is a more poetic way of saying that the sky got dark and it started to rain.

Choice of Words: Clouds are the white fluffy things in the sky. Covered means hid. Sun is the big bright thing in the sky that gives us light and warmth. Heavens is a poetic way of saying sky. Opened up means started to rain.

Related Expressions