"Is it windy?"
Translation:Est-ce qu'il y a du vent ?
du = de + le. Using de + [article] is often translated as "some", so il y a du vent means "there is some wind" - not a lot of wind, but more than a little wind -> "it is windy".
Using the "some" qualifier often helps you understand when de is needed in a sentence, like "she is eating bread" - elle mange du pain = "she is eating some bread."
When "she likes bread", then "she likes some bread" changes the gist of the sentence, so you wouldn't want to use de, and the correct translation is elle aime le pain.
French almost always has the article, sometimes adding de in front of it, and only drops both before names Elle aime Henri and some places elle adore Paris, but not countries *elle aime la France."
Since it's a question you can use the inversion method to state it. Just as you can say "voulez-vous danser?" instead of "vous voulez danser?" by inverting the subject and the verb, you can do the same for "y a-t-il du vent".
You take "il y a du vent" and switch the subject and the verb but the "y" has to go first. Then because french hates having vowel sounds from seperate words together, you stick in the "t" as a buffer between the "a" and "il". So you get "y a-t-il".
You would normally say "il y a du vent" which literally translates to there is wind. To use it as a question, you need to reverse the order of the subject and the verb, so you end up with " y a il du vent." The t comes in because of how you can't have "a il" as it sounds awkward to say, just like how you say "mon amie" instead of "ma amie." The t in this case has no meaning.