Post depth should generally be equal to half the height. Clean 3/4” in the bottom of the hole can help especially if you have poorly drained soils. If you are on clay maybe go deeper. If you’re going to use concrete and you’re on sand, you’ll be fine with 3’. Better yet use a ground screw, there’s very little surface area for the frost to push against.

Called today, they do all the closing season work in the next three weeks. Not the best time to go. Found another place

Looks like the off season permit link is disabled until November