As long as horse is up there before winter is in full force, August would be fine to move in. I trailered up here to MO from LA, (lower Alabama) in September, and horses did fine, haired out well, and came through bad winter just great.
Contact several of the companies around you and see if any are trailering anything else up, TB's or STB's move around all the time to tracks, or back home to their farms, so should not be too hard to find someone to haul.
And can put message out on FB groups to see if someone that will be down your way in August, showing maybe, could trailer back, for you.
Horses make me a better person.