What is de function of -t- in this sentence?
It is just a filler to make it sound nice. Also happens with "a-t-il?" and "aime-t-elle". Anytime between two vowels I think.
<Est-ce qu'il y aura du vent?> is also accepted, but <Y aura-t-il du vent ?> seems to be the more common way of saying this?