If you want to decorate with something, do it! I promise that on your deathbed. You won't say, "I wish that, back in 2017, I'd waited a few more weeks to decorate my cartoon bakery with fall trees."
Follow your bliss.
A lot of my neighbors have started adding fall things and redecorating. One leaves Halloween & Christmas up, together, all year.
September is good to do fall. October 1, Halloween. November 1, Thanksgiving. Day after Thanksgivibg, Christmas. That's how I do the house.