Look at these sentences:
Il y a du soleilIt is sunny
Il y a du ventIt is windy
Il y a du brouillardIt is foggy
Il y a de l'orageIt is stormy
Il y a des nuagesIt is cloudy
Il y a de la pluie aujourd'hui.It's rainy today.
Il y a de la brume.It's misty.
To talk about the weather in French, you will use Il y a + du / de la / de l' / des + noun. (Literally: there is some ...).
Note that du / de la / de l' or des agree with the noun following.
Case of il fait du soleil or Il fait soleil: This seems to be presented as idiomatic in a lot of French learning methods, and to be perfectly honest, some French people use it. However, it is not good French and still sounds clunky and child-like to many French ears (including mine!).
Il fait should always be followed by an adjective, and il y a used with nouns.
Note that you could also use Le temps est + adjective (ensoleillé, pluvieux, nuageux, brumeux, orageux) instead of using il y a + noun.
BUT there is no adjective for brouillard (fog), or vent (wind).
See also Talking about the weather with il fait + [adjective]
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