"How does it snow?"
Translation:Il neige comment ?
As far as I understand, those "t"s appear when an inversion would make something difficult to say quickly without a pause. Basically, in French, people don't like stopping or taking pauses, so if I ask:
"Does he have an apple?" = "A-t-il une pomme?"
Without the "t" there, the "a-il" would be very clumsy to say quickly.
That example is the easiest to see, but that is what is happening with "neige-il"... it is a bit hard to say it so a "t" gets put in front of the "il" so it is pronounced like "till" which makes it come out more quickly following "neige"