Bonjour yellamaraju, Indeed in French you can use both sentences, "C'est nuageux" and "Il y a des nuages", to express "It's cloudy" in a general way. "Il y a des nuages " can also simply means "There are some clouds", like for example in the sentence "Il y a des nuages dans le ciel.".

Bonjour John ! Though it seems that some people use it, "il fait nuageux" isn't correct in French. You'll prefer "Le ciel est nuageux" or "Le temps est nuageux", or "C'est nuageux" :) Bonne journée !