I started the TransAm last year on Sept. 15th, so if you leave right now it's not too late. I did get a lot hail, freezing cold nights, and snow but survived and had a great time. Was also very lucky that none of the roads I went on were closed yet due to snow. Also the campgrounds start closing after Sept. 1st so even though you may know of a campground up ahead, it may already be closed for the year. Much better idea to do the Pacific Coast route or Southern Tier.