Is it right to be overcast?

Incorrect, the correct word is cloudy.

Cloudy, China idiom, pinyin is w ū yú n mü bù, which means dark clouds cover the sky. Describe the cloudy weather.

Idiom usage: as predicate and adverbial, used in weather, etc.

Make sentences:

1. Today is sunny, and soon it will be cloudy.

2. The clear sky was covered with dark clouds in an instant.

Suddenly, the sky was overcast and thunder was loud.

There were dark clouds in the sky and it began to rain soon.