How do you change the following sentence to the future tense?: The sky is cloudy.
One option is "The sky will be cloudy".
There are two forms of the future tense which can be used in this context.
If you are making a prediction you can say "The sky will be cloudy tomorrow". This uses the future tense of the verb to be "will be".
If you are more certain you can say "The sky is going to be cloudy tomorrow". This uses the present tense of the verb to go (is going) and the infinitive of the verb to be (to be).