Ground grade below window

[block]

We are going to have two windows in a concrete block wall that will have back fill (dirt) then sod placed on top of that dirt just below these two windows.
My question is how close can I backfill the dirt to the bottom of the window ?
Is there an industry standard ?
I don't want the grass so close that I cant mow or weed trim without getting debris all over the glass. On the other hand I want to backfill as much as I can.
What is a good close but safe distance ?
Thanks

[Sweep]

If possible, rade should not be above the interior floor and any glass within 18" of the interior floor must be tempered. Otherwise, common sense should prevail.

[block]

Thanks Sweep.
I think I've decided to keep the outside dirt grade somewhere between 18" to 24" below the windows. I hope that will do the trick.
Thanks again.